A cookie is a string of information that a website stores on a visitor’s computer, and that the visitor’s browser provides to the website each time the visitor returns.
The website uses two cookies to bypass the password entry portion of the website for users already logged in to the website. If the website recognises that you have valid, non-expired cookies when trying to access an admin page of the website, you go directly to the administration interface. If you don’t have the cookies, or they’re expired, or in some other way invalid, the website will require you to log in again, in order to obtain new cookies.
These cookies contain “hashed” data, so you don’t have to worry about someone gleaning your username and password by reading the cookie data. A hash is the result of a specific mathematical formula applied to some input data (in this case your username and password, respectively). It’s very hard to reverse a hash (bordering on practical infeasibility with today’s computers). This means it is very difficult to take a hash and “unhash” it to find the original input data.