If you want the game here's the link: http://www.minecraft.net/ The game is not free. It's now in beta and costs 14.95€. when it's complete it costs 20€. You will get multiplayer option, so you can play online on servers with your friends.
Minecraft is a building and exploring game. You will start in a randomized world, with no items and your bare hands. In minecraft u can make alot alot of stuffs like: Ladders, Tools(Pick-axe, shovels, axes...), and aloooot and aloooot of other stuff. You can choose what you want to do. Some people are choosing to build alot and other are exploring caves and stuff. Here's a link to a minecraft page where you can find everything about it!: http://www.minecraftwiki.net/wiki/Minecraft_Wiki