Google Hangouts is a unified communications service that allows members to initiate and participate in text, voice or video chats, either one-on-one or in a group. Hangouts are built into Google+ and Gmail, and mobile Hangouts apps are available for iOS and Android devices.
Google Hangouts can also be a useful and cost-effective collaboration platform for enterprise customers. Hangouts also has an option called Google Hangouts on Air, which allows Google+ users to broadcast video calls live on YouTube. Hangouts on Air has gained traction as a free way for organizations to conduct online seminars and talk shows.
Google Hangouts replaces the previous chat capabilities built into Google+ and Gmail, as well as the standalone Google Talk app. Hangouts can also integrate with Google Voice, allowing users of that service to make free domestic phone calls from their computing devices.
As of this writing, the protocols that support Google Hangouts are proprietary.