In its endeavor to rebuild its Messenger to conquer the top chat Apps like Line, WeChat, KakaoTalk and others, Facebook in November 2013, launched a separate Messenger App for its users. This either could be used as a stand alone chat App or messenger got opened on touching the Messenger tab on the main Facebook App. Users always had a choice of not downloading it and continuing their chat in the main Facebook App.
But according to Techcrunch, soon Facebook will be sending notifications to its chat users to download Facebook Messenger App to continue their Facebook chat on their device.
Facebook is trying to acquire a higher position in chat Apps with this new move and its acquisition of WhatsApp.