What information do cookies hold?

Answer 1

They mostly contain readable text, though the exact contents depend on what sites you visit. Cookies often contain log-in information, so that is how sites know you are still logged into them. They may also contain navigation information.

Answer 2

Cookies on your computer store browser information. This is commonly done when you hit options such as "Remember me" or "Remember this users" when signing onto accounts. You can always clear your cookies via your internet browser settings.