Community is a comedy about a study group at a community college. The group is led by Jeff, an ex-lawyer, who starts it by accident with Abed, a young lad obsessed with films and pop-culture, whilst trying to flirt with a female student called Britta, check out the trailer below.
I first heard about it from the internet comic book artist Rogo (check out his stuff here), but I didn't take the time to watch the series, until I saw a video of Karen Gillian talking about the show and how it parodied of Doctor Who.
I was also told once, before I'd watched Community, that it was better than The Big Bang Theory - another comedy I think is very good. Now, having watched the first and second season of Community, I'd personally say that they are quite different. Community's tone and humour is somewhat darker and crazier than Big Bang's. It isn't afraid to deal with the issues in life, but at the same time things usually turn out alright,and there are sweet and innocent moments of fun in there as well - mostly from Abed and Troy.
One of the things that set Community apart though is that it is very meta - a word the TV show has actually taught me - which means its very self-referential. Like films about the process of filmmaking, Community draws your attention to how TV shows work, as they do it themselves. This is neatly done through Abed who likes to view live as a TV show. So for example, when it looks like the group is going to be stuck in a room searching for a pen Abed announces it must be a bottle-episode - or low budget episode as we might term it in the UK.
The show also uses lots of references, as mentioned before, and some of the best ones are when the whole episode is used for spoof, for example the episode Modern Warfare is an amazing war film/apocalypse tribute.
So in short, if you're into comedy, film and television references, or just Chevy Chase, I suggest you check this out.