I was wondering what function evil mode ran when I pressed :w. I tried using C-h k and then I pressed :w but it only registed the : I pressed and showed me information about evil-ex function instead of showing me what function is run when I save the file using :w.
It's evil-write.
As you know, : call the function evil-ex, You can try to find related evil-ex-* variable which save the association list of command bindings and functions and I found it's evil-ex-commands.