Minecraft is pretty awesome, but it is hard to explain exactly how it works. Â There is no official trailer, but here are a few fan-made ones that do their best:
Emergent gameplay:
Inception/Epic music Trailer:
*UPDATE*
Rock, Paper, Shogun has an excellent series of articles journaling the first few days of play.
http://www.rockpapershotgun.com/tag/mine-the-gap/