The new format is actually easy to understand. Instead of having 32 teams in 8 groups, we have a league consisting of 36 teams in it. No groups anymore. The rules are the same with the Champions League new format like @imamusma mentioned the details. I hope it'd be fun. I'm not even sure if there was any need for such format change but anyway we'll see. 

The last champion is Atalanta. It was a really unexpected ending while Leverkusen were destroying every single team ahead of them. For now I'm hopeful about Manchester United this season.