There are Four types of Drivers.
1)Type 1 that calls native code of the locally available ODBC driver.
2)Type 2 that calls database vendor native library on a client side. This code then talks to database over network.
3)Type 3, the pure-java driver that talks with the server-side middleware that then talks to database.
4)Type 4, the pure-java driver that uses database native protocol.