`which ls` and `help ls` will show you, if it is similar on your system.
"man echo" on linux describes /usr/bin/echo "help echo" describes the builtin.
on the othe hand, "man command" on mac os x gives a huge manpage of builtins (still hard to search for the common word "command")
`which ls` and `help ls` will show you, if it is similar on your system.