Minecraft is an adventure/survival indie game with its main focus being a sandbox title, a place where you can build, or do, anything. Minecraft is currently on PC, Mac, Android, iOS, and Xbox 360 as a physical and downloadable title. It will be coming to the the Xbox One in the future. The game was created by Marcus "Notch" Persson, and later further developed by Mojang, the company that Notch made. The Xbox 360 version was ported by 4J Studios.
There is no story and the game can go on indefinitely, this isn't to say it's boring by any means. You can explore the world and discover many different things. There are several different biomes you can find, Jungle, Desert, Plains, Forest, Tundra (or winter), Mushroom, and my favorite is the Extreme Hills. You can find villages with villagers running around in a few biomes. Best thing is that you can build anything, as long as you have the materials.
There are three different game modes that can be used: Survival, Creative, and Adventure. Survival is how you would play the game normally, collect resources to keep surviving and fight off monsters in the night and in caves. If you die, it's not the end, you can respawn where you last slept in a bed and continue but you will lose everything you had with you. Creative is self-explanatory, you have access to all the items and blocks and create anything from some mechanisms to a entire world full of quests and treasure. Adventure is way different than the other two game modes, you cannot break most blocks and mainly just admire the scenery. Adventure is the main game mode that is used on custom built maps, or worlds. People have made mods, maps, and custom textures for Minecraft. They are able to share them online through downloads.
Now everything I have talked about up to this point is available on the PC/Mac versions. The Xbox 360 version does not have an Adventure mode, and no way to share worlds unless by invite. Oh, you have to have Xbox Gold as well. The iOS and Android versions are farthest behind, but that's to be expected. The Xbox 360 and mobile versions do not support mods, maps, or custom textures. They do, however, have a unique crafting menu where you just have to have the items required and find the recipe to make another item. The PC/Mac version is slightly different in which you have to guess at what the recipe is.
All versions can have multiple players on the same world, with some exceptions. The PC/Mac version requires you to set up a server, unlimited players can join one server. The mobile versions require you to have local connections, I am not sure how many people can be on one world. Lastly, the Xbox 360 version requires an internet connection, Xbox Gold, and someone on your friend list who also has the game. It also only supports up to eight people.
Minecraft constantly has bugs that can exploit the game. While Mojang fixes them, every major update creates new bugs which can do the same thing. There are a few more issues when multiple people are on a server, a lot actually. With more people, more lag becomes apparent, especially when redstone is involved. Regardless, most bugs/issues are a result of lots of people on a single server.
Everyone has their own opinion on Minecraft, I think it's pretty good. However, ^. I, personally, give Minecraft a 4/5. So Minecraft gets a Silver Star.