Mainly used to save some information when surfing the Internet, such as login information.

Some forums can choose to remember the password when logging in, so that you don't need to re-enter it every time you log in. That's what Cookie do. Other websites can record their preferences when visiting websites. For example, Google search can choose how many articles to display per page. Cookie can be saved for a long time, and you don't have to set them every time.

If you don't like recording your status on the website, delete it. There is no other harm.