I have a task in which we have to provide Google sign in functionality for the aem community website just like OOTB facebook and twitter.
So what should be my approach after user login with Google.
Should I create a community user under /home/users/community?
If yes how? (Any reference )
You should follow a similar structure as FB/Twitter. That is use "/home/users/community" .For more details, refer to 
 Social Login with Facebook and Twitter
Thanks jaideep but i am looking for internal implementation .