To understand DNA testing for genealogical purposes, it begins to make sense when it is used in context of a news story. Below are three stories: The discovery of the bones of Richard III, the woman who claimed to be Anastasia, and Oprah traces her roots.
The Social Life of DNA by 
Genealogy DNA tests are inexpensive and non invasive. Tests are done at home. The package is mailed to the laboratory and results can be available in a matter of weeks.
There are three types of genealogical DNA tests;
autosomal (atDNA) test for all ancestors,
mitochondrial DNA (mtDNA), tests a man or woman along their maternal line
Y-DNA tests a male along his direct paternal line.
The tests results will tell you what haplogroup you belong to and the percentages of ethnic mix based on the mutations in your DNA. It can match you with others who have similar DNA, or markers, and who may be distant cousins.
More and more companies are doing the test, but these are the four who started it.
After you receive your results, you can opt to upload them to GEDmatch.com. They will match your results with people from other DNA companies who have also joined GEDmatch.
