I was surprised to discover today that I have been incorrectly using ie where eg is correct. It seems ie is the Latin initials of "that is" and should be used to clarify a reference to a specific thing while eg is the Latin initials of "for example" and should be used when giving an example of something. I think I knew eg meant for example but I mostly used ie which I thought could be used in either way. A little disconcerting to find out you have been making a mistake for practically your entire life.
I blame my parents.