A Daily Task ingame - help

It means exactly what you thought, playing chess. I've read on Carl's site you need to play it for awhile (about 2 hrs) to fulfill the task and ponder moves doesn't count (though it will give you the focused moodlet to up the skill faster). I don't know about this personally since I haven't tried that branch, just from what I've read.

I found the answer in the comments at the bottom of this page:

The Sims 4 StrangerVille Military Career