Oddly enough, it has taken me until today to realise when to use I.E or E.G when trying to give an example!
Originally, I thought that they meant exactly the same thing, but it turns out they have slight differences which means that their application in a sentence is slightly different.
I.E is an abbreviation for 'id est', and essentially means 'in other words', whereas E.G is short for Exempli gratia', meaning example given.
Turns out I was using I.e as a substitute for E.G, although typically that wouldn't actually be correct
Are there any words or abbreviations that you realised you were using incorrectly?