Re: Dumb Question: What Exactly is "Extended Spring Training"?
It is basically just a season that doesn't count. There aren't exact rules, but most of the time they are playing games just like they would in the regular season. They do play against other teams.
No website covers it. I doubt you are going to find any 'rosters' for it either. I have seen notes from EST three times this year so far and that is the most I can remember, ever.