2D games are drawn in a two-dimensional space using two-dimensional objects. To represent its position, each game object will have an
x and a
y coordinate, but not a
z coordinate unlike in 3D games.
This can range from top-down games, like dwarf fortress, to side-scrolling ones, like platformers. It would refer to any games where the character / objects can move freely in two dimensions (e.g. left-right & up-down).