Answer:
   
   Any authoritative legal material that was not redacted as part of the
   Mishna is known as Baraitot. Often the Gemara (main part of the
   Talmud) will quote a legal source outside the Mishna; This is a
   quoting of a baraita. Everything in the Tosefta is Baraita by
   definition, although there is much material that is considered Baraita
   that is from outside the Tosefta. The word 'baraita' means 'external
   teaching'.