I love these to bits. IF you haven't seen them, I would recommend going straight to the DVD sets.
Basically, they are a novelty duo, and are playing fictonalised versions of themselves in this television series. They parody popular musical genres (these sections tend to be the funniest parts of the show), and play the rest of the show out as an ordinary situation comedy.
If you haven't seen it, you don't know what you're missing. Jemaine and Murray tend to be the funniest, but Bret's a good laugh.
https://www.youtube.com/watch?v=2IPAOxrH7Ro
https://www.youtube.com/watch?v=VzxDMDJUO7U