A preliminary inquiry is a hearing for a matter that is scheduled for trial (usually months later) where the crown prosecutor provides evidence and the judge decides whether there is enough evidence to require the accused person to stand trial.
A preliminary inquiry can be thought of like a “mini trial,” where witness(es), often including the complainant, testify and are cross-examined by the defence lawyer, and the judge decides whether the crown prosecutor has enough evidence to even run the trial. It is very rare that a judge will decide that there is not enough evidence to have the trial.
However, it is still often beneficial for an accused person to have a preliminary inquiry. A preliminary inquiry gives the defence lawyer an opportunity to see how strong the crown prosecutor’s case against the accused really is. Often, a prosecution witness will change their story between the preliminary inquiry and the trial, which can be key to a successful defence at trial.