n00b question: team selection vs. tactics

Can someone break down where team selection (i.e. players) and tactics differ? I went through and setup my players, saved that as my team selection, and then went about goofing around with tactics. However, it seems like sometimes, the tactics I make will change the players on the pitch. I don't know why. I don't want it to- I'd like to have the team selection set one way, then not have my tactics adjust my guys. Or, at least, just figure it out so I know what's changing what.

THANKS!

I don't really use it any more, but I think if you save a team selection, it saves the tactics too. So, if you save a team selection, then change the tactics, then pick that team selection, the tactics will go back to what they were when you saved the team selection, not what they were after you made changes. I hope that makes sense. I think that's how it works, or at least how it used to.