The purpose of a preliminary hearing is to see if the Crown has enough evidence to justify sending the case to trial.  This also gives the accused and the defence lawyer, a chance to hear the details of the case against the accused.  The accused does not prepare a defence at this point.

If the Crown presents enough evidence, the judge will send the case to trial.  If the judge decides there is not enough evidence, the charges will be dropped, and the case will not proceed.

Does the victim need to testify?

Yes, most of the time, the victim and other witnesses will have to testify at the preliminary hearing.  If the judge sends the case to trial, the victim and the witnesses will likely have to testify again at the trial.

If you are going to be a witness at a preliminary hearing, you may want to take a look at the Witness Tips - Before Court section of the site.