What is the difference between M.2 and PCI Express 2.0 x4?

Question

Iron

Actually, the whole question is formulated in the title: what is the difference between M.2 and PCI Express 2.0 x4? Is it one and the same?
I ask the consultant in the store, he says no, but reading the wiki one gets the impression that this is still the same thing.

Answer 1

I don't know which wiki reads your impression, but M.2 is a generic interface that, depending on the key, can provide both PCI-E and SATA and USB and other interfaces.
https://ru.wikipedia.org/wiki/M.2#%D0%A4%D0%BE%D1%...