There are three main ways for a defendant to bring a lawsuit to an end. Each involves a different level of proof – and of expense and hassle. It's better to get a lawsuit “disposed of” as early as possible. 

Here is a quick summary. 

Motion to Dismiss for Failure to State a Claim

What it is. The gist of a motion to dismiss is this: "Your honor, even if everything the plaintiff says in the lawsuit is true, he has not accused our client of doing anything for which the law provides a remedy."

Example. I sue you, and in my lawsuit, I accuse you of frowning at me. Maybe you didn't frown at me, or maybe you did. Even if you did, I can't sue you for that. So your lawyer would file a motion to dismiss my lawsuit on the ground that I had "failed to state a claim for which relief may be granted." (This type of motion is often referred to as a Rule 12(b)(6) motion, based on the rule of civil procedure that authorizes it.)

The upside. If you win (and you would, in the unrealistic example I provided), the case is over, subject to the plaintiff's right of appeal, and you got out of it cheap because you didn't have to go through discovery and motions and a big trial.

The downside. Because a motion to dismiss is filed so early, the court has to accept everything the plaintiff says as true and has to give the plaintiff the benefit of the doubt on pretty much everything. If the statute of limitations hasn't run out, and maybe even if it has, the judge might give the plaintiff "leave to amend," which lets the plaintiff rewrite the lawsuit so that it will state a legal claim. Sometimes the judge will dismiss some of the plaintiff's claims but leave others in the case, which means that the motion didn't end the lawsuit in its entirety.

If the defendant loses on its motion to dismiss, in whole or in part, the case goes back for litigation, including discovery, summary judgment, and possibly trial.

Summary Judgment

What it is. A motion for summary judgment is filed later, after both sides have filed their pleadings with the court, and after the parties have engaged in discovery (depositions, written questions and requests for documents, and the like).

Example. I sue you and say you fired me because I'm an over-40 female. Age and sex discrimination are clearly illegal, so my lawsuit has alleged some illegal conduct on your part, unlike my "frown" lawsuit. (A little more detail may be required for my lawsuit to survive, but that's a topic for another post.)

You can't say that my lawsuit fails to state a claim because it does, but you might be able to file a motion for summary judgment.

So you take my deposition, and in my deposition you get me to admit that my boss asked me to catch up on my filing and that I called him an obscene name and told him to drop dead. Then I went back to watching TikTok videos on my phone. I was fired that afternoon for insubordination and abusive language.

The upside. On a motion for summary judgment, you can present to the court my deposition testimony, your witnesses' testimony, and other evidence to show that "there is no genuine issue of material fact" that I was discharged for a legitimate, nondiscriminatory reason. The court will still have to side with the "non-moving party" (in this example, me) on any disputed fact and does not make any judgments about who is more credible. But the court can accept undisputed facts that are in your favor, and also accept your evidence any time my side of the story was "I don't know," or “I don’t remember.”

Your chances of success on summary judgment are usually better than on a motion to dismiss because you can tell your side of the story. If you win, the case is over, subject to the plaintiff's right of appeal. The court will not give me a chance to rewrite my lawsuit at this late stage.

The downside. You have to go through the time, expense and hassle of the discovery process before you file. And, again, the court is required to side with the plaintiff about any disputed facts.

(Although it is not nearly as common, plaintiffs can also win summary judgment and avoid a trial if the undisputed facts are in their favor.)

If a motion for summary judgment is denied, the case is not over. It just goes to trial. A party can lose on summary judgment and still win at trial.

Trial

What it is. Come on. You know what a "trial" is.

Example. I sue for age and sex discrimination, and you take my co-worker's deposition. She says that she heard the CEO say, "I do not want any old biddies over 40 working in this company, and I vow with every fiber of my being to get rid of them all, no matter what it takes. And that includes Robin!" The CEO denies that he ever said this, and insists that I was fired for calling him a bad word and telling him to drop dead when he asked me to catch up on my filing.

Here we have major "disputed material facts," right? If my co-worker is telling the truth, the CEO has admitted to age and sex discrimination. If the CEO is telling the truth, then he had every legal right to fire me.

So, with this fact dispute, the court cannot grant your motion to dismiss, and it can't grant your motion for summary judgment, either. This is what trials are for.

The upside. At trial, you will have the chance to tell your side of the story, even if I dispute it. The judge or a jury will hear both sides and decide who is telling the truth.

The downside. A trial is a gamble. Will the jury side with your CEO, or with my co-worker and me? Who knows?

True story: Years ago, we had a witness, a genuinely good guy. After the trial, we talked to the jurors and found out that they hated him and thought he was a liar because he had shifty eyes during his testimony. In fact, he was squinting because he was wearing the old-fashioned kind of "hard" contact lenses. (If you remember those, they were VERY uncomfortable.) In front of a jury or even a judge, things like this matter. On a motion to dismiss or summary judgment, they don't because everything is submitted in writing to the court, possibly with some live arguments by the lawyers.

In addition, a trial is the most time-consuming, expensive, and disruptive of these three options. Even if you win in the end.