This summary is not the rule. The rule text controls.
If you're the one making a claim in a lawsuit (whether that's the original case, a counterclaim, or a claim against another defendant), you can ask the court to decide the case in your favor without a full trial. This is called asking for summary judgment. You're basically telling the court there's no real dispute about the facts, so the judge can just apply the law and rule in your favor.
You have to wait at least 20 days after the lawsuit starts before you can make this request, unless the other side has already asked for summary judgment first. If they've made that move, you can respond right away with your own request.
You can ask for summary judgment on the whole case or just part of it. You also have the option to back up your request with sworn statements called affidavits, but you don't have to. The rule gives you flexibility in how you build your case for why the judge should rule without going to trial.