A cookie is a small text file that is stored by the computer when a website is visited by a user. The text stores information that the site is able to read in the moment in which it is seen at a later time. Some of these cookies are necessary to the site to work properly, while others are useful to the visitor because they can safely store such as user name or language settings. The advantage of having the cookies installed in your pc is that you no longer need to fill out the same information every time you want to access a site you visited before.
How can I disable cookies?
Each browser has its own way to disable cookies.
Here is a series of links to most common browsers official help pages: