Cucumber is a software tool that computer programmers use for testing other software. It runs automated acceptance tests written in a behavior-driven development (BDD) style. Cucumber is written in the Ruby programming language.[6][7] Cucumber projects are available for other platforms beyond Ruby. Some use Ruby Cucumber with a bridge into the target language (e.g. cuke4php and cuke4lua). Others use the Gherkin parser but implement everything else in the target language.[8] Cucumber allows the execution of feature documentation written in business-facing text. Capybara, which is a part of the Cucumber testing framework, is an example of a web based test automation software.

Cucumber has following components, Selenium webdriver, Gherkin, Capybara and Rspec

http://www.methodsandtools.com/tools/cucumber.php

Gherkin + Capybara + Rspec + Selenium webdriver = CucumberGherkin :It is a Business Readable,Domain Specific Language that lets you describe software's behaviour without detailing how that behaviour is implemented.Capybara : It simulates how a user would interact with a website.Capybara helps you test web applications by simulating how a real user would interact with your app.Rspec : It is a behaviour driven development where it fetches the ids from the inspected elements for running the scriptSelenium web-driver : It is a connecting mediator between the cucumber script and the browsers.