To compare and contrast the legs of a vertebrate with those of an invertebrate, focus on the presence or absence of a backbone, the number of legs, structure, and mobility. Vertebrates, possessing a backbone, generally have paired appendages that serve as legs, while invertebrates, lacking a backbone, exhibit a wide variety of leg structures or may even lack distinct legs altogether.
Your best source for this is to Google the two, read and read, then summarize in your own words explaining the difference.
