A Preliminary Hearing is when the prosecutor (i.e. District Attorney and/or Attorney General) must prove a prima facie case, which means they must show a crime probably occurred and the accused is the one who probably committed it.
Informally, this is usually when the prosecutor speaks with the defense attorney about a potential deal for the defendant to consider.
In Franklin County, all Preliminary Hearings occur at one location, which is known as Central Court. Central Court is held at the Court of Common Pleas located at 14 N Main ST, Chambersburg, PA 17201.