I’ve been reading through their docs[0] and FAQs[1] but cannot for the life of me understand how they can use SPC as a chord prefix, and also just type normal sentences on a keyboard.

I don’t want to try it, but I do want to know.

0: https://www.spacemacs.org/doc/QUICK_START.html
1: https://www.spacemacs.org/doc/FAQ.html#how-do-i