Homogenous describes things that are all of the similar kind. If you have a homogenous group of friends, you probably wear the same outfits, talk the same way, live in the same kind of neighborhood, and like the same music. Boring.
Homogenous comes from the Greek for "same kind." It used to only mean people who had the same ancestors, but in English we use it for anything that is characterized by sameness. You might live in a homogenous neighborhood, where everyone makes the same amount of money and drives the same kind of car. The opposite of homogenous is heterogenous, which means "many kinds."