Isometric projection
A parallel projection where the three axes are equally foreshortened — fake 3D with no perspective and no vanishing point.
In true isometry the axes meet at 120° and nothing shrinks with distance. In games, "isometric" almost always means the cheaper 2:1 grid (really dimetric): diamond-shaped tiles stacked so that depth is implied without a single perspective calculation.
Q*bert (1982) opened the genre; SimCity 2000, Diablo and Age of Empires cemented it. The appeal was economic — you got a sense of space from ordinary 2D sprites and one sorting rule for draw order, long before hardware could do real 3D.