If you check the "Keep me logged in" box when logging in, you will not have to log in again the next time you come back to 0.APP on the same computer, even if you've closed down your web browser or turned off your computer since the last time you visited. This is a convenient option if you're the only one who uses your computer and you don't want to have to log in each time you visit us.
If you leave the box unchecked when you log in, you will automatically be logged out the next time you close down your browser or computer, and you will have to log in again when you return to 0.APP. This is the best option if you share your computer with other people, or if you are working on a public computer (such as at a library or at school).
Whether or not you check the box to stay logged in, you can always choose to log out of 0.APP by clicking on the "Logout" link in the upper-right of the page. Once you sign out, you will have to go through the login screen the next time you return to 0.APP.