A good example is Amazon.  If you place items in your shopping cart and turn the machine off without paying, the cookies will allow your items to stay in the cart until you return to shop again.

Some myths that surround cookies are they generate pop ups, they are used for spamming, they are only used for advertising, they are like worms and viruses because they erase data from the hard drive, and they are like spy ware that can get at the personal information on the computer.

They are always in the form of data, not  a program code.  They do allow for seeing the web pages viewed by a certain user.  They are stored on your hard drive as name-value pairs.

You can set your browser settings to accept or not accept cookies on your computer.  There are usually two lists involved.  The white list contains acceptable sites.  The black list is sites tht are not acceptable by the user.  You can also reject cookies from certain sites, not allow cookies from a third party site, accept cookies that expire only when the browser closes, and you can view and delete individual cookies that shouldn't be there.  Some browsers have a cookie manager so the user can delete cookies stored in the browser itself.  You can also choose an option in your browser so it will inform you each time a website send name-value pairs to you.  You can then accept or deny the pairs.

Erasing cookies is as simple as erasing all of the temporary Internet files on your computer.  You then lose all your cookie files.  So when you go back to a much visited site, the site will act as though it has never seen you before and assign a new cookie to you again. 

People or family members who share a computer also get their share of problems from cookies.  If I go to Amazon and purchase a book, my son can log in right behind me and use my account to purchase another book.  If you are using a public computer, like at a library, anybody can come behind you and buy stuff with your credit card.  Always make sure to check and see if stores have a warning posted about this on their site.

Or say you have 2 different computers you use.  One at work and one at home.  You will have to set two different controls for each one.  What you use on your home computer, you may not use at work and vice versa.  It can be quite cumbersome to reset everything if the cookies become a problem.

Cookies can be helpful for some and a pain for others.  Know how to use them to your advantage.