Encryption has become more important today for all of us than any other time in the History. But, many services, including Facebook’s messaging application, don’t support encryption and therefore are weak in providing security of our online data, which could result in data breach either by cyber criminals or by our own Government under surveillance programs. Facebook Inbox Messages or Chat between the two are protected by Secure Sockets Layer (SSL) encryption over HTTPS Channel, but the problem is it only encrypts data between user and Facebook. Facebook has access to the plain text of those conversations directly from their database.
Source: https://thehackernews.com/2014/05/cryptocat-offers-end-to-end-encryption.html