An IFrame (Inline Frame) is an HTML document embedded inside another HTML document on a website. The IFrame HTML element is often used to insert content from another source, such as an advertisement, into a Web page. The IFrame below embeds the homepage of this website. Try to interact with the IFrame by clicking on a button on the IFrame homepage. You need to instruct your tests to 'switchTo()' to the IFrame and then when you're done, switch back to the main webpage.
This is automationtesting.co.uk within automationtesting.co.uk
Cool Fact - this was the first ever video uploaded to YouTube :)