For three reason's, you can check the logged in activity. Log will show the information such as country location(Ex: USA, INDIA, etc.,) and Browser type(Ex:- IE, Firefox, etc.,) as well as operating systems.
To know, follow the below steps:-
- Login with your facebook account.
- Click the Gear Icon → Account Settings.
- Now you will be in General page. Click Security → Edit the Active Sessions.
Thats it. Now you can see your logged in activities. End All Activity will sign out for all other locations.