Cookies are small text files placed on your device when you visit a website. They allow the site to recognize your browser on later visits and to remember certain preferences. Cookies are not programs and do not access your files or personal data on their own. They simply store small pieces of information that the site can read again.
A cookie holds a short label and a value. When you load a page again, the browser sends that label back to the site, which is how the site knows whether you have an open session, whether you have already dismissed a notice, or which language and display settings you chose last time. Nothing more happens in the background: a cookie cannot run code, cannot read your documents, and cannot start a process on your device without the site asking the browser to do something on your behalf.
Alongside cookies we may use similar storage such as local storage in the browser, which works in a comparable way: a small key and value kept for a defined period. Everything that follows in this document covers both, unless the sentence names cookies specifically.