Minecraft is a game where you create your own entertainment.
In the game of Minecraft, you are a character in a world randomly generated and completely composed of 1 m3 cubes. You have the ability to mine them, removing the cube from the map and adding it to your inventory. You have the ability to place them from your inventory back into the world. And lastly you have the ability to craft them into different items and objects. This is the core of and almost entirely all of the gameplay. There also happen to be a few wandering enemies and creatures, but they are a rather small part of the game.
It's a box of Legos.