Question

How does a somatic cell mutation differ from a germ cell mutation?

Answer 1

Somatic cell mutation only affects the cells that cell gives rise to via mitosis...so a damaged skin cell only gives rise to other damaged skin cells. A mutation in a germ cell, however, is passed on to the progeny. So if the mutation is in the egg or sperm, the offspring will then carry the mutation.
So, only germ cell mutations are inherited.