You'll need a JDBC driver that works with the actual database that you are about to connect to. DbVisualizer works with any category (type) of JDBC driver even though it is easiest to use a type 4 driver (also called light weight driver or pure Java driver).
Drivers for some databases are bundled with DbVisualizer. Please check the JDBC Driver info for the actual database(s) on the Databases and JDBC Drivers page for more information.