Contained in the nucleus of each cell are twenty-three pairs of chromosomes. Twenty-two of these matched pairs of chromosomes are called “autosomes,” while the 23rd pair determines your sex (male or female). Autosomal DNA is inherited from both parents, and includes random contributions from their parents, grandparents, and so on. Therefore, your autosomes essentially contain a complete genetic record, with all branches of your ancestry at some point contributing a piece of your autosomal DNA.
Autosomal DNA tests can be used to search for relative connections along any branch of your family tree. Unless the connection is so far back that the shared DNA has essentially been eliminated through too many generations of recombination, any autosomal match between two individuals indicates a possible genetic connection. There is nothing in this test that will tell you which branch of your family the match is on, however. Therefore, having your parents, grandparents, cousins, and other family members tested will help you to narrow down potential matches.