Linux help command
Display information about builtin commands.
Displays brief summaries of shell builtin commands. If PATTERN is specified, gives detailed help on all commands matching PATTERN, otherwise the list of help topics is printed.
help [-dms] [PATTERN ...]
|-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.|
Display a brief description of the builtin shell command echo.
man — Display the manual page of a given command.