Signing in
Google sign-in. There is no separate password.
Active sessions
Every device currently signed in is listed, with its device, location, when the session was created and when it was last active. The one you are reading this on is marked This device.
The list is for review. There is no per-device sign-out from this page: if you see a session you do not recognise, sign out on that device, or revoke the app's access from your Google account, which ends every session at once.