Social Login is how all users log into their site. When you are invited to manage your group's site, or you've just created a site for your group, you have three options to log in:
Google (your gmail or Google+ account)
Facebook
LinkedIn
When you grant permission to Alumni Spaces to access this account, you are not enabling us to post anything on your behalf and we will not be able to log into your account. You are simply linking your Alumni Spaces user profile to your Facebook, LinkedIn or Google account.