Cookies are small, usually randomly coded text files that help your browser navigate a website. The cookie file is created by the site you are browsing and is accepted and processed by your computer's browser software. The cookie file is stored in your browser's local folder or subfolder.
When you visit the website that created the cookie file, your browser accesses the cookie file again. The browser uses the information stored in the cookie file to make it easier for you to navigate the website, among many other functions, by automatically allowing you to log in or reminding you of the settings you have chosen during previous visits to the website.