There does not seem to be one definitive definition of indigenous people, but generally indigenous people are those that have historically belonged to a particular region or country, before its colonization or transformation into a nation state, and may have different—often unique—cultural, linguistic, traditional, and other characteristics to those of the dominant culture of that region or state. (For more details, see this fact sheet from the United Nations Permanent Forum on Indigenous Issues

In some parts of the world, they are very few indigenous people, while in other parts, they may number into the hundreds of thousands, even millions. Over the years, many groups of people have been wiped out, either by diseases of colonizing peoples, or through policies of extermination.

Those indigenous societies that remain today are predominantly subsistence-based (i.e. farming or hunting for food for immediate use), and non-urbanized, sometimes nomadic.

via Rights of Indigenous People — Global Issues.