Also, Iran is mostly Sh'ite Muslim (so is much of Syria and a good deal of Iraq), while other Muslims are mostly Sunni.
Here's the CIA World Factbook's ethnic statistics for Iran:
Persian 51%, Azeri 24%, Gilaki and Mazandarani 8%, Kurd 7%, Arab 3%, Lur 2%, Baloch 2%, Turkmen 2%, other 1%
And it isn't just a modern difference. These language differences go way back, and also reflect different political histories within Islamic civilization. Islam started in Arabia, and was spread by conquest by Arab-speaking soldiers. Over the reign of the first few rulers, the new state, called the Caliphate (because its ruler's title was Caliph) was headquartered in Mecca, in Arabia near the Red Sea. After that the capital was moved to Damascus, it what is now Syria, where it remained for a long time. An Arabic nobility, based on the descedents of the first soldiers that backed Muhammad, led this Syrian headquartered, Arab state.
But the conquests extended far beyond the bounds of Arabic speach in those days. Clear across North Africa and into Spain toward the west. And into Persia and parts of central Asia to the east. The Sassanid Empire in Persia was one of the states overrun. Its populace converted. And soldiers recruited there - especially from a province in eastern Iran called Khorasan - entered the now multi-national army of the Caliphate. They were excellent cavalrymen and horse archers, in close contact with the traditions of the Asian steppe nomads, but civilized enough to have more discipline and loyalty.
Tensions quickly developed between the interests of the Arab nobility of Damascus and the Khorasani interest in the army. The Arab nobility was doing less and less of the fighting, while taking more and more of the revenue of the state. They were growing soft. The Khorasanis were doing more of the hard work and getting relatively little reward for it. Caliphs found they had to play balancer between these two factions to retain control of the army and prevent civil war.
This tension and a particular succession crisis led to one such war anyway, and the seat of the capital in the new dynasty moved to Iraq, half way between Damascus and Khorasan (Baghdad). At first the leading generals were Khorasani Persians while the Caliphs were Arabs. In an effort to preserve the balance, the Arab Caliphs recruited Turkish mercenaries, and later kept Turkish slave soldiers meant to be loyal to the Caliph alone, from central Asia, beyond Persia. So now the army had an Arab, a Persian, and a Turkish component. The Turks, however, were not nearly as disciplined as the Persians had been. They were also even better fighters.
The result after a while was that the Turkish slave armies became a sort of Praetorian guard for the Caliphate, and like the one in Rome before them, soon went into the ruler business. That is, they chose the ruler for subservience to themselves, instead of the other way around. Pretty soon the Turks were setting up and deposing Caliphs at will, and effective political control rested with the leading Turkish general (or Sultan - a title rather like Shogun in Japan, meaning the effective ruler based on control of the army, ruling de facto under a figurehead emperor). The Caliph had become a figurehead; still needed for Islamic legitimacy, but without effective political power.
Because the Caliphs being set up or deposed by the Turks were regarded as unreal in distant places, and out of Arab nationalism, various parts of the previously unified Islamic world broke away and became independent states. A dynasty called the Fatamids took over Egypt, and claimed the rulers they set up were the legitimate Caliphs. Berbers and Moors farther west set up their own states. Yemen, protected by the Arabian desert, went independent over a particular interpretion of Islam.
The role of the Arabs increased again, and an uptick in the unity of the Islamic world occurred, in reaction to the Crusades. Saladin, from a base in Syria, conquered Egypt from its rival Islamic rulers. And used the unified area thus created as his base of power to eventually throw back the Crusades. But he never controlled anything like the whole Islamic world. After the defeat of the Crusades, however, the Mongols came out of central Asia and conquered most of the eastern Islamic world.
This happened while the Mongols were still animist pagans. After the death of Ghengis, however, the Mongol empire broke apart into regional blocs, and many of the tribes that composed it, especially Turkic ones in central Asia, converted to Islam. The successors fought over the eastern Mongol empire, until Tamerlane succeeded in reuniting most of it under one state, centered in Turkic-speaking central Asia (north of Afghanistan), and extending through Iran, Iraq, and eastern Turkey. The wars involved in all this had devastated and partially depopulated that whole region, however. After Tamerlane, his empire went the way of Ghenis' before him, and everything was broken up into small competing warlords here and there. The Turks were firmly in political control of the area by then, but not unified themselves.
The Ottoman dynasty of Sultans changed that by unifying the Turks of Asia Minor and leading them to successful conquest, fighting Byzantium (the greek remnant of the eastern Roman empire). They took over all of the middle east, from the border of Persia, through Syria and Arabia, and including Egypt. Their own army was based in what is now Turkey, because newly won lands taken from Byzantium were used to settle the successful soldiers. Eventually they took Constantinople and made it their capital, renamed Istanbul. They then extended their empire into the Balkans, in a long rivalry with Austria, with the border swaying back and forth between Istanbul and Vienna.
Thus, the Turks in the Ottoman Empire came to rule essentially all of what we now call the Middle East. But they did not control Persia. The Persian speakers maintained an independence, going back to the warlord period, from the distance Turkish capital on the border of Europe. While all the Arab speaking area of the Middle East was under Turkish rule.
It was not until WW I that the Arabs became independent again. That was due to the British, who purposefully encouraged Arab nationalism as a way of unifying the various tribes under Turkish rule, to rise and fight against the Turks. Britain had long supported the Ottoman Empire as a way of containing Russia, but WW I changed that when Turkey sided with the central powers (which it did, because they were fighting Russia, and Russia was more of a threat than Austria then).
After the war, the British installed Arab kings on the thrones of most of the newly created countries of the Middle East, which had previously been administrative provinces of the Ottoman Empire. They kept Egypt for themselves because the Suez canal was important to their Indian empire. They let Jews settle in Palestine. Lebanon and Syria were given to Arab rulers but left to the tender overlordship of the French, who desposed the king initially given Syria (he got Iraq from the British instead).
I go through all of that to make clear the later differences in political history for Iran compared to the rest of the Middle East. Iran did not owe its existence to British arms, and had not engaged in a nationalist uprising against the Turks. Iran cooperated with Britain - and later with the US - through the 19th and 20th centuries, as a way of keeping out the Russians. A pro-western traditional monarchy ran the place as an important pro-US satellite in the cold war - a linchpin of the containment strategy directed at Russia - until 1979, when a violently anti-western Islamic revolution toppled the Shah.
Iran was then invaded by Arab Iraq, under Saddam. He thought they would be unable to resist effectively because of internal chaos from the revolution, but was totally wrong. Iran is a much bigger country in population terms, and even with poor tactics and less in the way of modern armament, Iran quickly got the upper hand. Throughout the 1980s, the two fought a bloody conventional war, as tough as WW I, with heavy use of poison gas by both sides, missle attacks against cities, etc. The Arab states of the gulf supported Iraq with oil money, because they feared Iran's Islamic fundamentalism for domestic reasons, and out of Arab nationalism against Persians.
The Iranians tried to cut off that supply of funding by naval skirmishing in the Persian gulf, and the US Navy went in to stop them. The US also provided intelligence to Saddam to enable him to hold off the Iranians. We would predict where breakthroughs would be attempted, and Saddam moved his armor to that area to met the attacks. With no way to stop Iraqi funding and after losing several conventional offensives, the Iranians eventually made peace with Saddam. He almost immediately turned around and attacked the Kuwaitis, who had been funding him throughout the war, but stopped once it was over. He wanted more. We stopped that, of course.
So when Iran looks back through history it sees a very different past than most of the Middle East does. They fought the Iraqis a dozen years ago. We were helping the Iraqis. Before that they threw us out and overthrew their pro-western traditional monarch. Before that they were non-occupied, well supported allies of the US, and before it of the UK, which backed their independence to keep the Russians out. Before the arrival of the UK, they were their own masters in a traditional monarchy. Iran is also Shiite Muslim, while most of the Arab world is Sunni Muslim.
This is very different from the experience of many of the Arabs, who were under Turkish rule, freed by the UK, desposed most of their pro-western kings in socialist revolutions not Islamic ones, often supported the USSR during the cold war, fought repeatedly against Israel, etc. And the Arab-Persian tension within Islam goes all the way back to some of the first political conundrums of the Islamic Caliphate, within a few centuries of its founding.
I realize this is probably far more than you expected with your simple "another sentence, please" question. But I figured some might find it useful.