Rekall is a database front-end. It is not itself a database -- data is stored somewhere else, in an SQL server, and Rekall is fundamentally just a tool to extract, display and update that data (of course, it does lots more than that, it does forms and reports and scripting and so on). It is database agnostic, and does not have any preferred database in the sense that Access uses the Jet database engine.
TheKompany is giving away a free copy of the packaged version of Rekall (normally costs $80 USD) to a lucky winner. Read more to participate to the competition!