What is Selenium RC?

Selenium RC ( Remote Control)  also known as Selenium 1. Selenium RC is the answer to a more powerful test suite for your applications. It follows the client-server model by allowing client libraries to execute tests on a browser controlled by the server.

Selenium RC was the main selenium component since a long time before the web driver merges brought up selenium 2. Selenium1 is still actively supported ( in maintenance mode). It supports  Java, Javascript, Ruby, PHP, Python, Perl, and C#.

It supports almost every browser out there. Selenium RC is great for testing complex AJAX-based web user interface under a continuous integration system.