Like Family Finder at FTDNA and the 23andMe test, it tests autosomal DNA. The downside is that its database will be small for a time. However, it is likely to grow quickly. It is also likely to have different participants than the other two, so you would want to test also at FTDNA when they have a sale, as suggested by Elizabeth.
23andMe has a good site to learn about the tests. It also has a demo. It also gives health-related results that the other two don't. The test that matches people is called Relative Finder. FTDNA has a much higher response rate, since 23andMe attracts a lot of people interested only in the health portion.