To be fair, search engines don’t help a lot in understanding this. There are a lot of explanations, the vast majority of which don’t seem to make sense to normal people.
Wading through them makes your eyes go glassy quickly.
I fully appreciate any Freeper who can give a better explanation than I could.
I did do an internet search as upchuck’s suggestion, and even though I minored in math and statistic’s, I am still not following the various examples.