It is best to choose a WikiName (like FirstnameLastname) as username to get your changes and signatures link back to your WikiHomepage. Your email is needed for you to be able to get notifications on page changes and to recover lost login data.
If you click on GetText(Create Profile), a user profile will be created for you and you will be logged in immediately.
GetText(Save) updates your profile (stored on the wiki server).
GetText(Logout) clears the cookie created at login.
The "ID", shown in the response page, gets saved as a cookie in your browser for the system to temporarily recognize you. It will expire next midnight - except if you choose GetText(Remember login information forever) (after being logged in), then the cookie won't expire.