Purpose:  to store state onto a client.
Example info:  Login/password, connection ID

The best review of cookies I know of is at http://www.cookiecentral.com/faq/#3.3  Go read that.  We'll talk from there.

Notes ...

• Cookies are optional.  The browser might not support them, and the user might have turned them off.  Of course you need not support such users.
• You can get arround the size limit.  Set a cookie like ID=10101010102.  Store into the datatbase what you need indexed by 101010102.  Remember to clean out the database every once in a while.
• Cookies take bandwidth to transmit, and are sent to every matching request wether you want them or not.
• Cookies stop proxy servers from caching!!!!
  
  
  
• Cookies cannot format your hard drive.
• Cookies cannot make you go insane.
• Cookies cannot reveil information you have not already told them.  It could share that info with other people in ways that suppise you.