YouPorn

YouPorn is a website allowing free access to pornographic video clips. It was founded in 2006, and has become one of the most accessed porn sites in the world. The site is free to access. It is financed using online advertising, such as banner ads. Users can upload their content (which are usually parts of porn movies). Each clip is reviewed, and is later released for public access. It is possible to search the site using keywords. There's also a paid subscription, where the users can access more content. 
Usually, people need to have a certain minimal age to be able to have access to pornography. The site does not verify the age of the person watching. For this reason, it has been blocked in many countries.