A little Dungeon Defenders help?

So I've just got the game on steam and I have a couple of questions:



1. What's the difference between online and local?



2. What's the campaign through this game? Like is it everything overall?



3. Is there anyway to find games with other people, besides for quick match which can put in in matches with different leveled character?



4. So I know the game is based on team play, but more often than not, you never find other players around your level on a map which is appropriate for you level. Any solution around that?A little Dungeon Defenders help?
The biggest difference I found between local and online private is that pausing the game on online private brings up the menu but does not actually pause.



I play with a group with levels from 1-70. We all have fun and work with the lower level characters by upgrading there stuff so they still get plenty of xp and level up faster.