Cookies are small text files sent to your browser by a website server containing information gathered about your visit to the site including, your log-in information, where you went, what you did, and any personal information you gave, that can be used to identify you individually on future visits.
Types of Cookies
Session cookies: These are temporary in nature, stored in memory during the browsing session and expire as soon as the browser closes. Session cookies can be used to gather information on how long a visitor stay on certain pages of a Web site, what browsers are used, what pages in the Website are more popular etc.
Persistent cookies: These are comparatively more permanent in nature, they have an expiration date ranging from couple of days to many years and are stored as a file in your hard disk. These type of cookies are designed to remain there until the set date has expired or until the visitor has deleted the file. The web site that placed the cookie also has the ability to extend the original expiry date without notice to the visitor.
First party cookies: These are those left on your machine by the web page that you are currently viewing. They can be either session or persistent cookies.
Third party cookies : These are those left on your machine by a domain other than the one that you are currently viewing. They can either be session or persistent cookies. The Third party persistent cookies are almost always evil, usually used by big advertising networks to track a particular surfer across different Websites enabling them to build a profile of that person for serving targeted advertising.