what is the difference btwn breed and species??

Species is a taxonomic term. Species is a group of organisms capable of interbreeding and producing fertile offsprings.

A species can have many breeds.

Breed is a term which is basically used in animal husbandary. 

Breed is a group of animals or plants with a similar appearance, behavior, and other characteristics that distinguish it from other animals or plants of the same species. Example: There are many breeds of dog such as labrador, pomeranian, pug, bull dog, etc.

Plant breeds are commonly known as cultivars.