/j is part of a tone/emotion tagging system over text. It means joking, hence what the ājā is standing for. So this tone tag is placed after a joke that was sent over text.
It is one of many ways to convey what the tone,
lightness, seriousness, and humor is used in a text. You place it at the end a message.
This system was created for and by
neurodivergent people who struggle to read the intended tone of something said over text, but everyone can and should use them. There are many others such as /
srs (serious), /s (sarcastic), /
lh (light-hearted), /hj (half-joking), etc.
/srs
HELP ME I CANT BEKIEVE YOU SHSJAJAKKSKA /j