What is a "motion"?
A motion is a formal request for a judge to make an order or ruling on an issue in a case. The parties can bring motions before, during, and sometimes even after trial. A motion may involve a simple scheduling matter, such as the prosecution's or defense's desire to postpone a preliminary hearing. (See Continuances in Criminal Cases.) Lawyers often make motions like this orally.
Some motions consist of written briefs that raise crucial legal issues. With substantial motions, judges often consider the lawyers' briefs, then later listen to their oral arguments. An example of a significant motion is one to suppress evidence, which typically asks the judge to rule that crucial prosecution evidence is inadmissible at trial because the police obtained it illegally. (See What is a motion to suppress?)