Facebook released a new standalone version of its Messenger app today. While the app still requires a Facebook account to use, it's separate from the rest of Facebook -- which might help keep you from being distracted by everything else happening on the social network.
The Messenger app looks a lot like the mobile apps, but bigger. You don't get a lot of communication options within the app, but you can set up notifications and mute specific conversations if you need to.
As you'd expect, you can also send stickers, photos and emoji as well. If nothing else, it will keep you off the rest of Facebook when you're just looking to send a quick email.