Cookies are small files which a website places on your computer. Each time you visit the website in the future your browser will send those files back to the website.
Cookies are also used to provide connections to Facebook, and add YouTube videos to the site. Those cookies are sent to those services, not to our website. If you're a user of Facebook or Youtube those sites could be aware of your visit to some pages on this site. If you would prefer that they not track this you can switch on "Do Not Track" functions in some new browsers, and some anti-virus software.