In a Google account (sync), what is the difference between Contacts and People details?

Question

For a Google account, you are allowed to sync Contacts and People details. What is the difference between these two?

Answer 1

The best explanation I could find online:

People Details is a new sync service related to the recent release of Google Play Games. It was pushed to most (if not all) android devices recently. Its purpose is to tie you together across all Google Play services (the separate services available from the Google Play screen). The idea is to maintain a uniform and unique "identity" for you in all related Google Games so that data from one can potentially be used to "enhance" the user experience in another

The contact sync is for the usual contacts that a user saves directly on your phone.

Answer 2

• Contacts is for syncing contacts with Google contacts. The information is the one specified by Android contacts (email, phone number, etc)
• People details is for syncing information with Google play and Google+, such as the Google+ profile picture, fit, Play game profiles, etc. The information is Google-specific.