To communicate with the Database using JDBC you need the following components.
JDBC DriverManager: The DriverManager class of the java.sql package manages different types of JDBC drivers. This class loads the driver classes. In addition to this, whenever a new connection establishes it chooses and loads the suitable driver from the previously loaded ones.
Note: From JDBC 4.0 the drivers in the CLASSPATH will be loaded automatically
JDBC API: It is a Java abstraction which enables applications to communicate with relational databases. It provides two main packages namely, java.sql and javax.sql. It provides classes and methods to connect with a database, create statements (quires), execute statements and handle the results.
JDBC-ODBC Bridge driver: This is a bridge driver which translates the JDBC method calls to ODBC function calls using this package you can communicate with the databases which uses ODBC drivers.