What is 'Eclipse'?
Eclipse is first and foremost an IDE for Java and C++. It is written in Java using IBM's Standard Widget Toolkit (SWT). The SWT uses native graphical widgets wherever possible, meaning that the result is a responsive and good-looking user-interface.
For Java programmers, the best thing about Eclipse is that it understands Java. It parses the source code quietly in the background as you edit, and highlights problems as it finds them. Forgotten an import? No problem, Eclipse highlights the unrecognised class before you started to compile. Overlooked a checked exception? Yet again, no problem - Eclipse will highlight the problem so that you can fix it right away.
The next best thing about Eclipse is that it allows you to set breakpoints in your Java code and will take you to that line of source code when the breakpoint is met in the running program. You can even set breakpoints for server-side code and step through it line by line. In fact Eclipse is excellent at managing the relationship between compiled classes, the corresponding source code, and the Javadoc. For example, if you're looking at a section of source code that references another class, highlight the reference and press F3 - you will be shown the source code of the referenced class. Allow your mouse to linger over a method call and you will be shown the Javadoc as a tooltip. These and other well-thought out features make Eclipse a joy to use. Well, most of the time. The truth is, Eclipse is a complex environment and it takes some getting used to. The learning curve is quite steep and it may take a while to become accustomed to it. But once you're there, you're there, and you'll be glad you made the effort.
Eclipse is available for free from the Eclipse website, as well as countless mirror sites around the world. Be warned that the download is rather large (up to 90MB), so choose your mirror carefully!