Concepts and need

Selenium Remote Control (RC) is a test tool that allows you to write automated web application UI tests in any programming language against any HTTP website using any mainstream JavaScript-enabled browser.

Selenium RC comes in two parts. 

1. A server which automatically launches and kills browsers, and acts as a HTTP proxy for web requests from them.
2. Client libraries for your favorite computer language.

Here is a simplified architectural representation....

Selenium Remote Control is great for testing complex AJAX-based web user interfaces under a Continuous Integration system. It is also an ideal solution for users of Selenium IDE who want to write tests in a more expressive programming language than the Selenese HTML table format.