What is the purpose of a preliminary hearing?

As its name implies, a preliminary hearing is sort of a
first step.  It is a step that is taken before an actual trial can be held. 
Specifically, it is a step taken to try to determine whether a trial can and should be
held in a certain jurisdiction.

In order to determine that
a trial can and should be held in a give jurisdiction, the preliminary hearing must be
held to determine the following things:

• Was a
  crime committed?


• Was the crime committed in an area that
  is under the jurisdiction of this particular court.


• Is
  there probable cause to believe that the defendant is the one who committed the crime. 
  This is not the same as finding the defendant guilty beyond a reasonable doubt -- it is
  just a finding that says that there is enough reason to
  believe that the defendant is guilty and that there should therefore be a
  trial.