help [-dms] [pattern ...]
Display helpful information about builtin commands.
If PATTERN is specified, gives detailed help on all commands matching PATTERN, otherwise a list of the builtins is printed.
Options: -d output short description for each topic -m display usage in pseudo-manpage format -s output only a short usage synopsis for each topic matching PATTERN
Reference: https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html#index-help