01In plain English
Screens mix red, green and blue light (RGB). Printers mix cyan, magenta, yellow and black ink (CMYK). Some bright screen colours cannot be printed, so print work is prepared in CMYK to see the real result.
02Why it matters when you are choosing
If you design for print, an editor without CMYK can hand the printer colours that come out dull or shifted. For screen-only work it does not matter.
03What to check
Ask the vendor
Check whether the editor can work in CMYK and export print-ready PDFs, or only converts at export.