Pretrial hearings are scheduled days and weeks before the commencement of trial. These proceedings are used by the lawyers and trial judge to review all outstanding trial issues.
Typically evidence and witness lists are exchanged. Motions and arguments are made and outstanding procedural issues will be resolved. The goal here is to get ready for trial.
Pretrial conferences are also used to negotiate a plea bargain. The prosecutor might give the defense lawyer a better offer if his or her client is willing to plead now. The defense lawyer may present counteroffers for the prosecution to consider. All the pretrial issues that need to be resolved before trial are settled here.