During a criminal trial in a United States court, a jury in most cases (or just a judge in rare cases) must make a determination based on applying facts and the law whether a criminal defendant is guilty of the charges against them. The finder of fact must make a decision of either guilty or not-guilty, based on each charge and the trial in which they view.
Likewise, a criminal defendant can plead with the prosecution in order to work out a deal outside of a criminal trial. Often, the prosecution will require that a defendant plead guilty to the charged crimes and in return, will recommend a reduced sentence for the judge. This has become the most common method of resolving criminal issues.
In a criminal case, in order to be found guilty, the finder of fact (the jury or judge) must find that the defendant committed the criminal acts beyond a reasonable doubt. This is an extremely high burden of proof, requiring that each jury member conclude that almost no doubt can be made the the defendant committed the acts. Other court actions, such as civil trials or police behavior, require much less burdens, such as burden by a preponderance of the evidence or probable cause.
A guilty verdict or plea will require a sentencing phase by the court, which may either be handled by the judge or by the jury in select circumstances. The sentencing phase is the determination of what punishment or rehabilitation the convicted person faces.