There are different kinds of human variation.
Some differences are biological or genetic, others are cultural or environmental.
There are also different levels of human variation. Some differences are at the individual level, others are at the population or racial level. The first distinguished us as separate individuals, the second distinguish a population of individuals as a separate race. In the system of biological classification called taxonomy a race is a subdivision or branch of a species, and a species in turn is a subdivision or branch of a genus. All populations which are capable of interbreeding with each other and producing fertile offspring are considered to be members of the same species, regardless how great their differences or how distinct their relationship.