There are special keywords like congratulations and rad that change colors and have animated effects appear on your screen when used on a Facebook timeline. Officially, they’re called Text Effects.
Here’s the Facebook trigger words in English (as of 12/07/17):
References for Facebook Text Effects
The lists of current Facebook trigger words (which is what I’d like to call them) are compiled from these 2 sources—
Facebook animated special words (Mashable)
All the Keywords That Activate Facebook’s Text Delight Animations (@owenyin) — this has a list of trigger words in other languages besides English
Note that these don’t work on every device or platform. They tend to work best on a desktop or laptop. Your mileage may vary on mobile browser, or mobile app, or iOS, or Android, or iPad.
From what I can tell, these Facebook hot words do not work in Messenger or private message; only in the timeline posts and comments.
Don’t like Text Effects on Facebook?
You can turn off text effects in your timeline posts and comments by selecting the pull-down menu on upper right, and select Remove Text Effects.
Why Facebook Introduces New Features
Why, you might ask? The overarching goal of Facebook is to increase the time people stay on Facebook. Once they have your time and your presence, they can do other things in front of you and behind the scenes. Or, as one of the Facebook founders, Sean Parker, has revealed:
“The thought process that went into building these applications, Facebook being the first of them, … was all about: ‘How do we consume as much of your time and conscious attention as possible?‘” … and “exploiting a vulnerability in human psychology.”