A Rubik's cube is a $3 \times 3 \times 3$ block of little cubes, called cubies, and any of its nine layers can turn. Twenty-six cubies show on the outside: eight corners with three stickers each, twelve edges with two, and one in the middle of each face with a single sticker. Those six never leave their faces, so each one names its face's color.
Here's one to play with. Grab a sticker and drag it to turn its layer, or drag the empty space around the cube to look at it from another side.