RSpec Testing (Request Specs, Feature Specs & Integration Specs)

I'm a Ruby on Rails developer and I'm currently learning RSpec. I've gone through basic Rails testing covered in http://ift.tt/MUotxZ that uses Rails built-in testing framework ActiveSupport::TestCase. There I saw Integration testing.

Then when I started learning RSpec and went through the rspec-rails documentation on http://ift.tt/1RVGOvz, there is talks about Request specs, which many Rails developers prefer using Capybara and FactoryGirl. But Capybara specs are placed under the spec/features directory.

So I'm really in a confusion with Request specs, Integration tests and feature specs. What does they do? Are they equivalent? What type of functions are tested in Request/integration/feature specs?

It'll be helpful if someone clears this,

Thank you.