Sign out when you finish on a shared computer, and end sessions on browsers you no longer use. A session is one browser signed in as you.
Logout ends only the session in this browser. Other browsers stay signed in.

The first row, marked "Current Device" (1), is the browser you are using now. Other rows show the browser name and when each session was last active.
In the row of the session you want to end, select Revoke (2).
The Confirm Logout dialog opens.

Select Logout.
The app signs that browser out, and the session disappears from the list.
If you revoke the "Current Device" row, the app signs you out here and opens the sign-in screen.
Use this if you think someone else has your password.
After you revoke all sessions, this browser also forgets your language and light or dark mode. Choose them again after you sign in.
To lock someone out for good, change your password as well.
See Change your password.
If you sign in on more browsers than your installation allows, sign-in shows the error "Allowed limit access" with the limit. To continue:
If you have no signed-in browser left, wait until an old session expires.