An H-Bot is a 2 Axis motion platform which uses 2 stationary motors to control a load on the X-Y plane.
It is so named because of the H shape the single belt makes as it loops around the frame. Because the design uses one belt to control both axes, H-Bots are extremely low profile.
H-Bots excel in quick, high precision motion. Because the motors are in a fixed position, there is less load inertia leading to faster accelerations and better position control. This technology can be found in commercial 3D printer platforms as well as high speed industrial machinery.