Lets just say for your sake you've heard of this game before, and if you haven't you were simply in a diabetic coma. If you have no idea what the fuck that green box guy is doing there its because you haven't heard of Minecraft. Minecraft is quickly becoming a huge hit with a ton of people for its simplicity and the ability to do whatever you want.
What is this game? Its a simple game made by a single man where you explore build and survive. The entire world is completely destructable and made of 1x1x1 bricks that you can manipulate to your fancy. Build huge castles made of glass or make a dick in the sand, the possibilities are endless. Then have all that hard work ended by a creeper whose sole mission is to sneak up on you give you a small heart attack and then blow the shit out of whatever you were making.
You can customize the world more by downloading player skins to change how you look to almost anything and by getting texture packs which greatly change how the entire world looks around you. These features are both totally supported in single and multiplayer.
So Minecraft is currently still in public beta and has no set release date as the creator is kind of making things up as he goes. It has singleplayer and multiplayer and i gotta say its fun as shit and you need to go see what all the buzz is about. During beta its 25% off the price of the game. Which is just 15 Euros which since i'm not some nerd economist i can't convert to USD without giving a fuck.
Seriously though, buy this play this, love this, then get pissed when you get creeper ambushed as soon as you find your first diamond and ragequit this.