How can I know whether user has logged in through facebook account or through Site login? How can I know whether user has logged in through FB or through site's login section? I am giving points to user based on FB login that's why It's important to know. Thanks
You could use Rules module together with Notification module, to achieve what you want. There is no out of the box solution for this problem.

You will have to look into Adding a new rule to react to user registrations
Or to user logins. You will properly have to create a custom module depending on the deepth of what you exactly need