'The social network has been experimenting with these for awhile — you've probably seen them on posts with the words "congratulations" or "xoxo" (or some variation thereof.) When posted, these words appear as a different color and clicking on them triggers a brief animation (balloons or hearts, for example.)
Now, Facebook is updating the list of words that triggers these animations. Additions include: "rad," "bff," "lmao," and "thank you so much." All of those words will now come with their own colors and animation effects.
Facebook is also updating the animations associated with reactions to "life events," like engagements and weddings. Now, when people add a reaction to a "life event," the reaction will come alongside animated reactions that fill the update. ' via Mashable