The grizzly bear is the North American subspecies of the brown bear.
Grizzly bear (Ursus arctos horribilis), Toronto Zoo.
The term grizzly bear can refer to any bear called grizzly or e.g. the Kodiak bear. Black bears and polar bears are different species from the brown bear or grizzly.
As I have mentioned earlier in the polar bear article grizzly bears and polar bears can interbreed in spite of being classified as different species. Their mixed offspring however has no legal status in terms of protection and conservation and such bears of mixed heritage are not considered by humans to be worth preserving.
Because grizzly bears are just about the scariest creatures one can encounter in the forests on this continent humans have worshiped them for ages with a religious awe. Art was created depicting grizzly bears and sometimes out of grizzly bear parts. The Toronto Zoo has various statues depicting grizzly bears around their grizzly bear exhibit.
Further Readings:
Grizzly bear on Wikipedia.
Grizzly–polar bear hybrid on Wikipedia.