A ceramic coating generally does the same thing as a wax or a sealant does, which is protect the paint from UV damage and environmental contaminants (rain/water spots, bird poop, tree sap, tar, etc.). The difference is that the ceramic coating is generally much more durable, lasting 2+ years due to the SiO2 in it's chemical makeup. A typical wax lasts 6-8 months, and primarily uses carnauba and other waxes as well as natural oils in it's chemical makeup. Application is different as well, with ceramic coating being a little harder to apply correctly, but still similar to applying wax. As a result, ceramic coating is more expensive to buy and install, while wax is much cheaper.
Some people say that waxes look like they give the paint more "depth", but I don't know if that's really true.