The arena is the place where TIO's languages are executed. The table looks as if it were providing shelter for the stick and the ball, which (analogically) symbolizes the arenas supporting the languages inside,
@a'_' - While the imagery is not unreasonable, I suspect that the only real significance of the logo is that it's a not-repelling rendering of the initials of T)ry I)t O)nline.
Dear @Dennis , I just want to say "hi" :) I have been code-golfing these past few days and I have been enjoying it a lot..m AND I have been using TIO, of course, and trying to learn Jelly ;) thanks for all you've done so far