> Celestial mechanics...don’t ask me more than that lol
The primary factor is the oceans on Earth. The Moon (and to a lesser degree the Sun) pulls the ocean water into what we call "tides". Similarly, the tidal "bulges" pull the Moon, and due to the friction of the water moving on the Earth surface, as the Earth rotates (much faster than the Moon revolves around the Earth), the bulges lead the Moon and actually speed it up a little bit.
Speeding up a satellite (like the Moon) does affect its orbit, specifically it raises the orbital altitude, thus the Moon moves farther from the Earth. It's only an inch and a half per year, but it means in about 600 million years the Moon will no longer completely cover the Sun during a Solar eclipse, so no more total eclipses.
But also, the same friction of the oceans is slowing Earth's rotation (that's where the energy to speed up the Moon comes from), and in around 200 million years, an Earth day will be 25 hours long, and eventually (billions of years, assuming the Sun doesn't give up first), Earth and Moon will become tidally locked at the same rotational rate, meaning the Moon will stand still in the sky.
Don't hold your breath. :-)
It’s not the ocean tides, it’s the tidal transfer of momentum — a body in prograde motion around a parent body loses rotational momentum as it pushes away, and vice versa. If the Earth had no oceans this would all still be going on.
The Earth has roughly 100 times the mass of the Moon, and the Moon has given up rotation first. The Moon obviously rotates of course, otherwise we wouldn’t see the same face all the time.
The Sun and Earth are similarly pushing away from each other.
Also the Earth’s tides are one third the product of the Sun’s gravity, despite the greater distance compared with the Moon.
The tidal bulge lags the rotation of the earth and has the effect of raising the level of the Moon’s orbit, which actually slows it down. The moon at 380,000 km orbital radius moves at about 1.0 km/sec. GPS satellites at about 23,000 km orbital radius, at about 3.8 km/sec.
The net tidal effect of the earth on the moon is a transfer of about one gigawatt - a billion joules per second - from earth’s rotation to the moon’s orbit.
The specific orbital energy, that is energy per unit mass, of a circular orbit is -μ/(2R), where μ is the main body orbital parameter, and R is the orbital radius. The negative sign means the two bodies are gravitationally bound. The specific potential energy of the orbit is -μ/R and the specific kinetic energy of a circular orbit is +μ/(2R). The -μ/(2R) is the sum of the two term. -μ/R + μ/(2R) = -μ/(2R). So, the moon is gaining altitude while losing speed.