Won’t like to confuse you by giving a very elaborate answer. Let me put it briefly. The SET (Social-Engineer Toolkit) is designed specifically to perform advanced attacks. Written by David Kennedy with much input from the community, SET was designed to be released with the www.social-engineer.org launch. It has now become a standard tool for penetration testing. SET helps execute targeted, focused attacks against an organization or person and can be used by hackers, both ethical and others.