As with most such distinctions, it's not quite clear cut. Basically, though, the orthodox are those who have come to some accommodation with modernity and Western culture. They participate in the general popular culture.
The ultraorthodox in contrast have pursued a fundamentalist enclave approach, trying to separate from the outside world. They have tended to extend Jewish religious law in ways that make them ever more distinct (like inventing the idea of "Glatt" kosher, i.e. extra-super-kosher) and emphasize the study of Jewish religious law as a supreme value.