It is an appearance before the judge, without witnesses and associated costs, to determine whether something must be done before the trial (or so the trial can continue).
A quick example is a drink driving charge. The defendant sttates there is a medical reason for him not producing a sample of blood or urine. The judge can order that his medical records are enough and nothing more needs to be done and the trial can continue at a future date; or he can order an independent medical exam is needed before the trial.