For all the times you’ve been chatting with a friend and have wanted to say “Okay” or merely show your approval, you don’t need to whip your keyboard out and type in the words. Facebook will let you show your approval with merely a click of a button on the Messenger app for iOS and Android.
Instead of the “Send” being grayed out when you have not typed anything, a thumbs up, or Like button has appeared. Now, instead of typing in “Okay”, “Alright”, or “That’s great, man. I approve”, you can simply hit the Like button and your friend will receive your approval as a Like button sticker.
The Send button now transforms into the Like button
Source … http://tech2.in.com/news/apps/facebook-adds-like-button-sticker-to-messenger/897224