What is a cookie elaborate on it using an example? ?

It is a little text file that a website can ask your browser to store on your computer. They aren't allowed to be too big, and you can always choose to ignore them (not store them).

They are used to add "persistence" to a website. When you come back the the same website, it can check the cookie that it left in your browser and see that you're the same person (and possible automatically log you back in).

A little file that holds your recent browsing history like how often you visit a web site.

Here is one (and it's kinda cryptic but it shows I visited xfx.com):

__utma

38492394.945257802.1227847110.1227847110.1227847110.1

xfx.com/

1600

444616832

30117558

696371728

29970707

*

__utmb

38492394

xfx.com/

1600

1507132544

29970711

696371728

29970707

*

__utmz

38492394.1227847110.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none)

xfx.com/

1600

3847630976

30007419

696841728

29970707

*

this wiki page on http cookie should answer everything you need to know about cookie

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