Tim Visher, who used to produce the popular VimGolf in Emacs Videos, has a couple of useful tips about using dired:
#emacs: In dired, `w` copies the file to the kill ring (and clipboard if you have that set up), `M-0 w` copies the absolute path to the file, and `C-u w` copies the relative path to the file based no the dired buffer's default-directory.
— Tim Visher (@timvisher) April 25, 2018
As a clarification, note that w copies the file name not the file itself into the kill ring. You can do several files at once by marking them.
I don’t think I’ve seen any of them before and they certainly aren’t on the dired cheat sheet that comes with Emacs. You can, of course, find the ‘w’ command in the dired help buffer but as far as I can see you have to check the documentation for dired-copy-filename-as-kill to get the information on the prefixes.