Selenium vs Fitnesse [closed]
Selenium is a web automation framework. It allows you to write code that "drives" a browser, so you can automate clicking through a site, filling in forms etc...
FitNesse is an acceptance testing framework - it is a tool to document acceptance tests as testable code. You can execute you tests and see whether they pass or fail.
The two are complementary to each other - you don't have to use Selenium with FitNesse or vice versa, but for testing websites, it is good to have your acceptance tests written in FitNesse (or a similar framework) and have them use Selenium to drive a browser.
Fitnesse is a testing framework that lets you interface with code written in a language of your choice through something they call a Fixture.
Selenium provides you with an api to drive the web browser for testing. Selenium provides a dll and probably a jar that you can use to hook into Fitnesse through one of these Fixtures.
Where I work we use Fitnesse to write web site tests that use Selenium to drive them under the covers.