A legal motion is a procedural device in law to bring a limited but contested matter before a court for decision. A motion may be thought of as a request to the judge (or judges) to make a decision about the case. Motions may be made at any point in the proceedings, although that right is regulated by court rules which vary from place to place.
A "motion to dismiss" asks the court to decide that a claim, even if true as stated, is not one for which the law offers a remedy. For example, a claim that the defendant failed to greet another on the street would be dismissed for failure to state a valid claim. A claim that has been presented after the statute of limitations has expired is also subject to dismissal. If granted, the claim is dismissed without any evidence being presented by the other side. A motion to dismiss has taken the place of the common law demurrer in most modern civil practice.
A "motion for summary judgment" asks the court to decide that the available evidence, even if taken in the most favorable light, does not support a claim. This motion can only be made when the time for discovering all evidence has expired. For example, a claim that a doctor performed malpractice by prescribing a drug would be subject to dismissal on summary judgment if the plaintiff failed to obtain expert testimony indicating that the drug was improperly prescribed. Motions to dismiss and motions for summary judgment are types of dispositive motions.
A "motion in limine" asks the court to decide that certain evidence may or may not be presented at the trial. For example, the defendant may ask the court to rule that evidence of a prior conviction that occurred a long time ago should not be allowed into evidence at the trial because it would be more prejudicial than probative. If the motion is granted, then evidence regarding the conviction would be prohibited from the trial.
A "motion for a directed verdict" asks the court to rule that the plaintiff or prosecutor has not proven the case, and there is no need for the defense to attempt to present evidence. This motion is made after the plaintiff has rested its case, and prior to the defense presenting any evidence. If granted, the court would dismiss the case.
A "motion for judgment n.o.v." (non obstante veredicto, or notwithstanding the verdict) asks the court to reverse the jury's verdict on the grounds that the jury could not reasonably have reached such a verdict. This motion is made after the jury's verdict. If granted, the court enters a new verdict. Typically, this motion can be used in a criminal case only to reverse a guilty verdict; not guilty verdicts are immune to reversal by the court. In U.S. federal criminal cases, the JNOV motion is unavailable; its function is served instead by the motion for judgement of acquittal.
Under Rule 50 the Federal Rules of Civil Procedure, the motion for directed verdict and JNOV have been replaced by the motion for judgment as a matter of law, which can be made at the close of the opposing party's evidence and "renewed" after return of the verdict (or after the dismissal of a hung jury).
A motion for new trial asks to overturn or set aside a court's decision or jury verdict. Such a motion is proposed by a party who is dissatisfied with the end result of a case. This motion must be based on some vital error in the court's handling of the trial, such as the admission or exclusion of key evidence, or an incorrect instruction to the jury. Generally the motion is filed within a short time after the trial (7-30 days) and is decided prior to the lodging of an appeal.
A "motion to set aside judgement" asks to vacate or nullify a judgment and/or verdict. Motions may be made at any time after entry of judgment, and in some circumstances years after the case has been closed by the courts. Generally the grounds for the motion cannot be ones which were previously considered when deciding a motion for new trial or on an appeal of the judgment.
A "motion for nolle prosequi" ("not prosecuting") is a motion by a prosecutor or other plaintiff to drop legal charges, usually in exchange for a diversion program or out-of-court settlement.