A cookie is a small piece of data that requires very little storage, sent from a website and stored on a user's device (usually a hard drive) while a user is browsing a website. A cookie is 'passive' and that means that it does not contain an executable software program, a virus or spyware/malware. A cookie is composed of two parts, its name and its content or value. The life-time of the cookie is usually set by the website and can last for anything between the length of the users session on a particular website or indefinitely. Technically, only the web server that sent the cookie can access it again when a user returns to a website associated with that web server.
A cookie contains information linked from a web browser (the user) to a specific web server (the website). If a web browser accesses that web server again, the web server can read from and react to that information. An example of this is when using an online store and putting items in the virtual shopping basket. The item information can be stored as cookies on your device so that if you cannot complete the purchase and need to return to the online store at a later time or date, the website can retrieve the items that you had in your basket from the cookie information stored on your device. This site also uses Google Analytics which stores cookies on the client device and allows us to track website usage which, in turn, enables us to make modifications to this site in order to deliver a much better user experience.
No. Cookies are completely passive and therefore cannot interact with your device. They do not have access to the information on your hard drive or any other storage media.
Yes. Browsers offer cookie management options within their tools. You can set the browser to accept cookies only from specific websites (e.g. this website). Browsers can also enable users to delete specific cookies. It is even possible to set a browser to reject all cookies. Note that choosing to disable all cookies could significantly affect your web browsing experience because many Internet services rely on cookies.