There are two meanings for Genetic Distance:

1. Genetic Distance is the number of differences, or mutations, between two
   sets of results. A genetic distance of zero means there are no differences in
   the results being compared against one another, i.e., an exact match. This is
   the meaning when comparing Y-chromosome DNA or mitochondrial DNA.
2. For autosomal DNA comparisons, genetic distance may refer to the size of a
   DNA segment. The genetic distance is then the length of the segment in
   centiMorgans.