I just read the description of FEN (*Forsyth–Edwards Notation*) and EPD (*Extended Position Description*), I have a basic idea of what they are, but I still have some points that are not entirely clear:

* What are the main differences between those two?
* When should I use one over the other one?
* Which one is more common to see?

I am trying to decide which one to use for a personal project, and I can't take this jump without knowing everything about them.