The major differences between Mahayana tradition and Theravadan tradition in Buddhism include the number of Buddhas, the proper language to use for religious texts, the number of bodhisattvas, and the acceptability of adaption of local custom.
Mahayana Tradition recognizes an infinite number of Buddhas who are able to help people achieve enlightenment or, for the lay followers, pray to in times of need. Theravadan tradition however only recognizes Gautama Buddha and prior Buddhas as legitimate. These Buddhas are accepted as men who found enlightenment, but not as supernatural beings. The Mahayanan tradition of accepting infinite Buddhas is beneficial to the religion overall because general practitioners can look to the different Buddhas for guidance and support in times of trouble which, in turn, has a profound positive influence on lay followers.
Theravada Buddhism only accepts Maitreya Bodhisattva as an “official” bodhisattva because he is the only one mentioned in the Pali language cannon.