Kassaundra is correct--each company basically targets certain features. I've most familiar with Ancestry DNA and it does not check health markers like 23 & Me, etc. Basically, it gives you information on what percentage of your markers are from different areas of the world. That can and does change a little overtime as more people enter their DNA and the pool to draw comparisons from enlarges. It does give you possible 1st, 2nd,3rd & 4th cousin matches (sibs too) IF they have also had their DNA tested--otherwise you do not get that info. It also lets you link to public record family trees on their site IF you pay their fee. Ancestry allows anyone to build their family tree in the site if a member, but most importantly, they have digitalized many, many records--ship manifests, census, military records, land titles, some newspapers, birth & death, marriage records. Anyone working on a genealogy should be verifying all information with records--technically if you don't have a verification you can not include it other than an aside.
BTW---Homo Sapiens all came from Zimbabwe AFrica (current name) and migrated to Middle East, Asia, Europe and eventually North America. Neanderthals started in Europe--4 yrs of Anthropology classes!