I got this one!
Perfect team is an online mode for OOTP where you manage a team online against other people. The games are simulated on OOTP’s servers, every 30 minutes (from 10 AM to 1 AM), M-F. Saturday and Sunday are playoffs and the crowning of a League Champion. Then it starts all over again the next Monday.
You earn PP (Perfect Points) for various achievements of your team. You can spend those to purchase more packs or to purchase individual players in an Auction House (where the players for sale are all placed by other people).
As @vyshka mentioned, they use a promotion/relegation model like soccer, so teams that do really well advance to higher (more difficult) leagues, and teams that do really poorly go down to easier competition. So the theory is that you’re competitive with your peers.