The CoreXY arrangement and the very similar H-bot arrangements are popular mechanical arrangement for a RepRap motion stage.
The CoreXY and the H-bot are a Cartesian arrangements -- they makes it easy to move the head in straight lines along axis 90 degrees from the other axis.
There is a small change in the belt pattern from the H-bot arrangement to the CoreXY arrangement. Some people say that the CoreXY arrangement is unconditionally better than the H-bot arrangemeng. "A Core-XY Implementation: overcoming H-Bot design drawbacks and building a laser-paper-cutter".
A CoreXY and a H-bot are a parallel manipulator system. In other words, the motors on a CoreXY system or H-bot system are stationary.
Parallel manipulator systems, such as CoreXY and h-bot and Dualwire-Gantry (DW-G), typically have much lower inertia than serial stackup arrangements. The lower inertia of a parallel manipulator system, when using the same motors and the same forces, typically gives more rapid acceleration than serial stackup arrangements. (For example, the Prusa i3, RepRapPro Mendel, etc. use a serial stackup -- in other words, some of their motors are pushed around by other motors).
- Kevin Craig. "So, you want to build an H-bot?".