I do know what it is, though I haven't seen it in action. I expect that in a few years time, my son will be playing it obsessively but as I've read quite a lot about the educational benefits of it, I will do what I can to encourage him :)
There is so much more to minecraft than just a game, or building, or blocks. there is a book called minecraft for parents. once i got my head round kids on computers and computers being part of their future i embraced it. my son is now interested in geology and i made up a crystal bag for him replacing diamond and other expensive crystals with same colour replacements, naming the stones and uses and also healing properties of both sets of stones / crystals - he now collects crystals. he now makes his own minecraft games and builds towns and mines for precious stones. best creation ever since lego...he recreates his computer minecraft in lego.