I missed that rushing. Here's some basic information https://www.tomshardware.com/reviews/glossary-m2-definition,5887.html#:~:text=2 slots.,more bandwidth than SATA%2C M. It goes over 3 types
M.2 (and NVME, kinda like a turbo-M.2) are insanely fast, you can get them at a decent price (30-60$ or more) but you sacrifice storage unless ya pay more, same as sata SSDs but just a hair more expensive. They do share the PCIE data lanes/sata ports (depending on mobo and which m.2 you get), so look it up for the motherboard you choose.