What are the main components of Selenium testing tools?

Selenium IDE, Selenium RC and Selenium Grid


Selenium IDE is an integrated development environment for Selenium scripts. It is implemented 
as a Firefox extension, and allows you to record, edit, and debug tests. Selenium IDE 
includes the entire Selenium Core, allowing you to easily and quickly record and play back 
tests in the actual environment that they will run. Selenium IDE is not only recording tool: 
it is a complete IDE. You can choose to use its recording capability, or you may edit your
 scripts by hand. With Auto complete support and the ability to move commands around quickly, 
 Selenium IDE is the ideal environment for creating Selenium tests no matter what style of tests you prefer.

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.

A server which automatically launches and kills browsers, and acts as a HTTP proxy for web requests from them.
Client libraries for your favorite computer language.
The RC server also bundles Selenium Core, and automatically loads it into the browser.