There are two main types of cookie, Session cookies and Persistent or Tracking cookies.
Session cookies are only stored for the duration of your visit to the site and are used to pass information from one page to another, for example to retain items in your shopping cart before checkout. These cookies are deleted when your browser is closed.
Persistent/Tracking cookies are kept on your computer hard drive and collect information about your activity on the site and how you use it, user preferences, settings and information for future visits. These cookies can be read by the website when you visit again.