A cookie is a small file delivered by a website to your computer, tablet or smartphone, where it is stored, It contains information about your visit to the website and is stored in your browser so the server can retrieve that information later on. Some cookies are only used to store settings and others, called tracking cookies, are used by advertisers to track you across sites and find out what you view online, thus serving you advertisements that match your interests. You can browse the Internet and stop all cookies from being permanently stored by using private browsing mode. The downside of this is that you will have to set up again website settings for that site, like for example turning off a search engine safe search or an Internet board cookie that allows you to access the website without having to enter your username and password every time you visit.
Flash player also stores cookies in your computer, they have the .sol extension and, unlike Internet browser cookies, Flash cookies are very difficult to manually locate and erase, specialist data erasing software is needed for this. There isn't a standard Cookie length duration, this depends on the server sending it to you, many tracking cookies tend to last years, if you run antispyware scan in your computer tracking cookies should be detected as harmful as they menace people's privacy.
On Windows systems, there is a directory of cookies. All recent browsers include the two-click availability of erasing all cookies, and emptying the browse history (remember your internet dervice provider conserves the URLs of all Web sites you visit, use a VPN) and cache (cookies are not the only Web site files you receive).