In a civil lawsuit, a plaintiff asks the court to order the defendant to do something. Whether the court can and will grant the plaintiff the relief sought depends on whether the court has the power to do so and whether the plaintiff proves entitlement to it.
Whether the court has the power to grant the requested relief depends whether the plaintiff has brought a valid recognized cause of action (as well as whether the court has personal and subject matter jurisdiction). Every cause of action consists of elements that the plaintiff must prove with admissible evidence in order to prevail. Broadly speaking, this is essentially a check list. For instance, generally speaking in New York in order to win a breach of contract case a plaintiff must prove four elements: 1.) that a valid and enforcable contract exists between the parties, 2.) that the plaintiff performed its obligations under the contract, 3.) that the defendant did not perform what it was required to do under the contract, and 4.) that as a result the plaintiff suffered damages.
If the plaintiff proves each elements required by the particular cause of action presented, then the plaintiff may recover. What happens in court is the presentation of testimony and documents which parties try to get admitted into evidence, in order to prove or disprove the required elements.
