DreamSpark editions are for students. Microsoft gives free MSDN Downloads access to students in select countries under DreamSpark.
The top one, or the one below it if you are in the UK. The rest are not something apparently you need to worry about lol Enterprise versions are same as the top two, except have Windows To Go, DirectAccess, BranchCache, and AppLocker etc for enterprise solutions.
debug/check builds are for people who work with system drivers and anti-virus programs and such. It comes without runtime improvements and helps the developers squash the pesky bugs.