The goal of the Java programming language is "write once, run everywhere". Java
was developed to be a robust object oriented programming language that would run
on a variety of different types of computers.
If you have ever been frustrated that the same program that runs on a Macintosh
at work or school does not run on your PC at home, you have run into the problem
that Java was designed to solve. Java runs on Macs, Windows, and Unix. It also
runs on many other devices, such as handhelds and embedded devices that control your
car, your household thermostat, or your telephone.
Applets are small Java programs designed to run inside of a web browser. The Java programming
language has built-in features for design of Graphical User Interfaces. The
combination of a standard language for designing interfaces with the ability to
run on browsers on many different types of computers has led to the widespread
use of Java Applets as a way of providing interactive web content.