What is Eclipse?

Eclipse (http://eclipse.org/) is free and open source multi-language software development environment. It can be used to develop applications in Java, and in other programming languages (C, C++, COBOL, Fortran, JavaScript, Perl, PHP, Python, etc).

 

Eclipse is probably the most known development Java environment, and it contains a large set of plug-ins that expands its functionality, like the integration with Java EE servers.

History

Eclipse began as an IBM project. In 2001, a consortium was formed to review this tool and develop it as open-source software. The original members of that consortium were Borland, IBM, Merant, QNX Software Systems, Rational Software, Red Hat, SuSE, TogetherSoft and WebGain. By the end of 2003, the number of members increased to over 80! In 2004 the Eclipse Foundation was created, and Eclipse 3.0 was released.


Versions 

Each year the Eclipse Foundation and its projects release a new version on a coordinated schedule. This release is called the simultaneous release, coordinated release, release train, or annual release of Eclipse. After each coordinated release, there can be several follow-up service releases (SR1, SR2, …).

The coordinated versions also have project names. For example, the latest release 4.2 is called Juno. Before that, 3.7 was called Indigo. Two more versions are already planned: Kepler (4.3) and Luna (4.4).

No need for more details, you can learn all about this tool in this links:
 - EclipseProject 

 - Wikipedia