What is Facebook Messenger?

Facebook Messenger (sometimes abbreviated as Messenger) is a free instant messaging service and software application which provides text and voice communication. Integrated with Facebook's web-based Chat feature and built on the open MQTT protocol, Messenger lets Facebook users chat with friends both on mobile and on the main website.

Facebook has reported that Facebook Messenger has reached 1 billion monthly active users. David A. Marcus heads Facebook Messenger, having joined Facebook by invitation of Facebook CEO Mark Zuckerberg.