A cookie is a bit of software that collects and stores data.
A cookie might save your login information in the browser so that you don't need
to fill it in every time you revisit a website. A cookie might also save your
preferences, such as whether you want to share your information with certain
advertisers.
To inspect which cookies you have stored, use the Web Developer Tools (F12) and
click on storage. Sometimes you may need to expand the Web Developer Tools
bar to see this option, or press on the arrows to see the hidden options.
