What is it?

Sorry for the akward question but I couldn't find the answer. Is it a game? is it a program? It looks fun :D.

It is "After Action Report"

So basically it is just a story detailing what happened during a game. The usual appearance of the term has been for Victoria AARs detailing the progress of creating an empire.

Yes, it's originally a military term that transferred first into wargames and then into general strategy games (I'm old enough to remember reading board wargame AARs in magazines like Fire and Movement)

I went to a few AARs while I was in the Army - not much fun but a good learning experience. Which is exactly what they are used for in games.