What does that message mean on WhatsApp?
The message says: "Messages you send to this chat and calls are now secured with end-to-end encryption." It adds that you can 'tap for more info', which we're assuming most people didn't do.
The long and the short of it is this - WhatsApp have added encryption to all of its services, which includes text-based messages, voice calls, and group chats. This is on iOS and Android platforms, which means it is very, very difficult for any authorities and governments to see what you're talking about with anyone.
Unless you're handing out your password and phone to people, you and the recipient are the only people who can read your messages - even WhatsApp can't see what you're talking about.
WhatsApp says: "From now on when you and your contacts use the latest version of the app, every call you make, and every message, photo, video, file, and voice message you send, is end-to-end encrypted by default, including group chats."
"The idea is simple: when you send a message, the only person who can read it is the person or group chat that you send that message to. No one can see inside that message. Not cybercriminals. Not hackers. Not oppressive regimes. Not even us."
So there you have it. Expect a lot of services to start telling you things like this, what with the arguments between the FBI and Apple kicking off royally, last month.