Bifocal contacts lenses have two prescriptions in the same lenses. Multifocal contact lenses have a range of powers in each lens. Multifocal contacts also is used as a catch-all term for all contact lenses with more than one power, including bifocal contacts.
Bifocal contacts lenses (like bifocal eyeglass lenses) have two powers - one for seeing clearly far away and one for seeing clearly up close. Multifocal contact lenses, like progressive eyeglass lenses, have a range of powers for seeing clearly far away, up close and everywhere in between. ("Multifocal" is also a catch-all term for all lenses with more than one power, including bifocals.)