End-to-end encryption essentially blocks anyone beside the parties communicating from accessing a conversation. Popular Facebook-owned chat app WhatsApp is among the other services that offer end-to-end encryption for calls and texts.
"End-to-end encryption has become an industry standard for real-time communications such as messaging -- and now, we're bringing it to phone calls, right from your Phone app," Google said in a blog post. "Calls between two Android phones on Fi will be secured with end-to-end encryption by default, so you can have peace of mind knowing your calls are staying between you and the person you're talking to."
You'll know a call is encrypted by hearing a "unique ringing tone" and seeing a lock symbol on the screen before you're connected. That lock symbol will show up on the screen during a call, too.
End-to-end call encryption will first become available for one-to-one calls between Android phones using Fi in the coming weeks. Messages by Google already encrypts one-on-one texts and chats between parties using Messages and that have chat features enabled.