The import reserved word is required to make use of existing classes in other packages. In order to use the Applet class in your code, you must import it by stating

import java.applet.Applet;

or

import java.applet.*;

The first method imports only the Applet class (from the java.applet package). The second method imports all classes in the java.applet package. There is no performance penalty for importing all classes in a package even when only a few will be used.

import is similar to include in C.

Book: 2.5, pg.74