A set of classes providing the implementation of the interfaces that are part of the JDBC API is called as JDBC driver.
The vendors of JDBC drivers provides the classes as part of a jar file.
Example:
1.ojdbc14.jar oracle driver from oracle corporation.
2.mysql-connector-java-3.0.11-stable-bin.jar (Mysql driver from MYSQL Lab).

The vendors of the JDBC drivers provides the name of the Driver class,Format of the JDBC URL in the manuals/documentation provided by them.

Examples of JDBC Driver:
com.mysql.jdbc.Driver from MYSQL Lab.
oracle.jdbc.driver.OracleDriver from Oracle corporation

Examples of JDBC URLS:
1.jdbc:mysql://localhost:3306/TEST(jdbc url format of mysql LAB’s Driver.)
2.jdbc:oracle:thin:@ localhost:1521:XE(jdbc url format of oracle’s Driver.)