Can you define “Force play situation” (see Rule 10.09)?

When a kicker puts a ball fairly in play and becomes a runner, this “forces” any runner on the base immediately ahead of the kicker to advance, as it does any runner on the base immediately ahead of a forced runner. Runners so forced are no longer safe on the base they originally occupied, until and unless a runner or kicker behind them is put out.

Note that a runner’s requirement to tag up before advancing on a caught ball (10.05) does not constitute a “force” in this sense. When the 3rd out of an inning is made on a runner failing to tag up, that does NOT nullify any runs scored on the play prior to the out being made, unless it was the scoring runner put out in this fashion.