factory_girl
is used as substitute for test fixtures, to generate objects with predefined data for use in tests;
capybara
is a integration testing tool;
faker
generates sample test data;
guard-rspec
works with guard
, an automated testing tool;
launchy
takes web pages generated by integration tests and opens them in a browser
You can get a better idea what each gem does by finding it on Github and perusing the README. If you're looking for an introduction to RSpec, the RSpec docs are a good place to start. There are a number of tutorials that address testing -- eg. this one.