A cookie is a small text file that the website you are visiting requests to save on your computer. Cookies are used on many websites to give visitors access to numerous functions. The information in the cookie can be used to monitor a user's surfing.
There are two types of cookie. One type saves a file for a long period of time on your computer. This is used e.g. for functions that indicate what is new since the user last visited the website in question. The other type of cookie is known as a session cookie. This cookie is stored temporarily in your computer's memory while you are surfing on a page, e.g. to keep track of the language you have chosen. Session cookies are not stored for a long period of time on your computer, but disappear when you close your browser. (Source: Swedish Post and Telecom Authority (PTS), www.pts.se)