The type builtin is useful for this. It will not only tell you about aliases, but also functions, builtins, keywords and external commands.

$ type ls

ls is aliased to `ls --color=auto'

$ type rm

rm is /bin/rm

$ type cd

cd is a shell builtin

$ type psgrep

psgrep is a function

psgrep () 

{ 

    ps -ef | { 

        read -r;

        printf '%s

' "$REPLY";

        grep --color=auto "$@"

    }

}

type -a cmd will show all the commands by that name in order of precedence, which is useful for the ls alias above, where the alias itself calls ls.

$ type -a ls

ls is aliased to `ls --color=auto'

ls is /bin/ls

This tells you that when you run ls, /bin/ls will be used, and --color=auto will be included in its list of arguments, in addition to any other you add yourself.