Secret Conversations will only be seen by the sender and receiver
It's a feature most messaging apps have, and now a version of it is coming to Facebook Messenger.
You'll soon be able to send Secret Conversations, an end-to-end encrypted way of contacting people. That means only you and the person you send the message to will be able to see it, it's impossible for any middle man to see it while it's sending or after it's sent.
This level of encryption is not going to be throughout all of Messenger, but just in certain conversations you establish.
The message you send will also only be readable on one device. Most people who use Facebook and Messenger regularly could be using it on their laptop, phone, tablet, or any combination of devices. By only sending it to one device, you're closing down who can see it even more.
Each message can also be timed, similar to sending a photo on Snapchat. After the time period you set it for, the message will be deleted forever.
Facebook is only testing Secret Conversations at this stage, but expect it to become an integral part of Messenger in no time.