Selenium automates browsers.
Primarily it is for automating web applications for testing purposes.
Which part of Selenium is appropriate for me?
Selenium IDE Logo
If you want to
create quick bug reproduction scripts
create scripts to aid in automation-aided exploratory testing
Then you want to use Selenium IDE; a Firefox add-on that will do
simple record-and-playback of interactions with the browser
Selenium LogoSelenium Grid Logo
If you want to
create robust, browser-based regression automation
scale and distribute scripts across many environment