type

type tells us if the command is aliased or not. an external executable. 

$ type grep
grep is hashed (/usr/bin/grep)

$ type echo
echo is a shell builtin

$ type perl
perl is /home/vagrant/localperl/bin/perl

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

$ type ll
ll is aliased to `ls -alF'