What is the meaning of cookies in internet browser ?

http://en.wikipedia.org/wiki/HTTP_cookie

A cookie is a small text file that contains some pertinent information about you and the website you are viewing.

Most cookies help you keep track of usernames, passwords, and what you have in your shopping cart while shopping online. Cookies are not executable programs and cannot contain or spread viruses.

Some cookies are used to track advertisements that have been displayed in your browser. This is so that you don’t see the same advertisement repeatedly. There are some cookies that keep track of your browsing habits but they do not identify you personally. Still, some people find this to be too intrusive and opt to disable cookies as a good measure.

Deleting the files in the cookie folder theoretically gets rid of your cookie files. Nothing bad will happen if you do this.

Many browser-based applications that you run when you connect to a web site want to "remember" you and your likes, dislikes, personal information and other details. They write this information in a "cookie" that's written to your hard drive. They're harmless. They help the applications start faster and give you more "personalized" service. Remove them and the sites have to start over.

Basically, it's junk that gets on your computer from the Internet, like fake offers and security threats. I remember on old versions of Windows (like 95, 98, Millennium, 2000), there was a Cookies folder on the C drive where you could put all that stuff so it just stayed there without doing anything.

They are basically tracking devices of a website ;)