An earlier instant messaging (IM) service from Google, introduced in 2005.  Google Talk provided text messaging and voice calling for Windows, Android, BlackBerry and ChromeOS devices.  Nicknamed "Gchat" and based on the XMPP/Jabber protocol (see 
Jabber), Google Talk provided a link to the user's Gmail account and displayed the number of unread messages in the inbox.  It was also a component of the Google Apps package (see 
Google Workspace).  In 2015, the Google Talk client programs were discontinued although third-party apps that use the XMPP protocol are still supported.  See 
Google chat.