Two Dimensional Camera Motion
The camera used to depict the game state moves with two degrees of freedom. That is, the camera can move up and down, left and right, and zoom in and out. Such cameras cannot tilt or pan like real world cameras, as they lack a real third dimension. (They have height and width, but no depth. Pivoting the camera on a point, like in a tilt or pan causes changes of camera angle that require three dimensions to represent properly.)
Strong example Metroid [Nintendo, 1986] presents the game world to the player in two dimensions, the camera view following Samus as she moves through the play field. The camera moves on a two dimensional plane, up, down, left or right.
Strong example While Double Dragon [Technos Japan, 1988] presents the game state using a two dimensional camera, though the gameplay takes place in three dimensions. The camera can move up, down, left or right, but never moves in or out along the game world's z axis.
Nintendo, developer (1986). Metroid. Nintendo, nintendo entertainment system edition.
Technos Japan, developer (1988). Double Dragon. Tradewest, nintendo entertainment system edition.