What are cookies?
Session or persistent cookies
Some cookies are session cookies. This means they’re deleted when you close your web browser (Internet Explorer, Firefox, Safari etc.). These are the cookies typically used when you log into a bank or make an online purchase. Other cookies are persistent which means they remain on your computer until they expire. This can be a fixed time after you have visited the website or a particular date. These cookies are used to remember information between visits to a website. For example, if you tell the BBC website to remember which weather forecast you want to see, it will use a cookie to remember that.
First or third party cookies
First party cookies are set by the site you’re visiting. In the example above, the cookie would be set by the BBC. They’re only read when you go back to the same site again.
Third party cookies are set by someone other than the site owner. These may be set by agencies who have placed adverts on a site you visit, by analytics programs that help site owners know how well their site is working and similar organisations. If you go to another site that uses the same advert provider, the cookie may be read again, and the advertising agency will be able to recognise that the same computer has visited this site too. This information is generally used by agencies to target adverts, so you’re more likely to see adverts for products you are interested in.