What is the Messenger app and why am I being asked to install it?

Messages are moving out of the Facebook app and over to the Messenger app, so now we'll be asking people to install Messenger and start sending messages from there instead.
The Messenger app lets you:
Reach friends wherever they are now
Text your friends for free using your existing data plan
Reach friends on their phones and the web, so they never miss your messages
Know who's seen your message, and who hasn't
Easily message friends or start a group conversation
Share photos, videos, stickers and more
Include friends of friends in conversations
View your most important group conversations in one place
Get right to your messages
Access your messages and chats wherever you log into Facebook
Get free push notifications on your phone or tablet, so you see each message as soon as it arrives
Quickly switch between multiple conversations with in-app notifications
After you install Messenger, all of your messages and contacts will be waiting for you in the app. You can also still see your messages on the Facebook website. Open a web browser from your computer or phone and go to www.facebook.com.
How to get the app:
We'll keep giving you links to install Messenger, and soon you'll see a reminder notice where you'd normally see your messages. At that point, you'll need to install Messenger or go to www.facebook.comfrom a browser to view and send messages.
If you'd like to install Messenger now, it’s available on iOS, Android, Windows Phone and some feature phones. To get the app, go to fb.me/msgr or visit the app store on your phone or tablet