What is CoreXY, and why does it matter for print speed?

In a CoreXY printer, two stationary motors drive the print head across both the X and Y axes together through a crossed belt system, instead of one motor per axis moving a heavier gantry.

The practical result is a lighter, stiffer moving assembly, which lets the machine accelerate and change direction faster without shaking itself apart or blurring fine details.

That's a big part of why most of today's genuinely fast enclosed printers — the kind that print in under an hour what used to take four — use a CoreXY layout rather than a traditional bed-slinger design.