OPK Tests detect Ovulation?? Meaning WHAT Exactly??

Okay so i have been taking the opk Test this whole week which is or was (not sure if it's ended) my "fertile" week.

What does the opk Test detect ..?

Ovation, right? So does that mean I am most fertile when I test positive? Or does it mean I should BD before I test positive? Or after?

I attached me Wednesday results and today's results... which day was I supposedly most fertile?

I AM SO LOST!!!! HELP

DO I HAVE A BETTER CHANCE OF WEDNESDAY OR THURSDAY?

I only ask because I used preseed last night & not today..

So I'm a little worried/bummed :(