When you use this service, you provide a URL of the page you want to test along with information, such as what browsers you want it tested in. The app then configures a new VM with the OS and browser you specified, and returns the test results in the form of screenshots, videos, logfiles, text, etc. You can then step up a gear, using an API to access functionality programmatically, which means that such apps can be combined with task runners, such as your own local Selenium environments and others, to create automated tests.