The halo effect is a cognitive bias whereby the perception of one trait (i.e. a characteristic of a person or object) is influenced by the perception of another trait (or several traits) of that person or object. An example would be judging a good-looking person as more intelligent.
while stereotyping is a popular belief about specific social groups or types of individuals. eg.. Filipinos are good english speakers, so if you find a Filipino walking in your place,, you will assume that he/she speaks english well, though you have no proof that he is a good english speaker..