Aboriginal Americans (or alternatively, American Aborigines) are the aboriginal (original residents) peoples of the Americas. They include the Native Americans and the Alaskan Natives. The more commonly used terms for these people are Native Americans and American Indians.
The Native Americans are called First Nations in Canada. And Alaska Natives' relatives in Canada are the Inuit. Together, they are sometimes called the First Peoples.
See "Native American" for a detailed description of the various nations/tribes of indigenous peoples to the Americas, and other terms that attempt to denote the same.
Part of the reason this term is used is because most of the people now living in the Americas are descendants of people who moved there from Europe.
