Understand `compgen` builtin command

From help compgen: $ help compgen compgen: compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C command] [-X filterpat] [-P prefix] [-S suffix] [word] Display possible completions depending on the options. Intended to be used from within a shell function generating possible completions. If the optional WORD argument is supplied, matches against WORD are generated. Exit Status: Returns success unless an invalid option is supplied or an error occurs. **What do options [-abcdefgjksuv] stand for?** In other words, I want to know how to use all options.