During a trial the functions of the Judge and those of the Jury differ in basic, but important roles.
The Judge will oversee that the court proceedings are followed in accordance with the law. He, or she, will preside the case and decide on applicable law for each specific case. They rule on the admissibility of the evidence to be presented, on the scope of the witness testimony and reliability of the expert witness. Those decisions made by a Judge regarding the admissibility of the evidence to be presented to the Jury if often done without the presence of the Jury. A Judge determines which of the evidence to be presented to the Jury is pertinent to the case, admissible by law and reliable.
The Jury decides on the veracity of the evidence presented during trial, the credibility of the witness and make a decision based on those. This decision is based based on the facts presented to them during the trial. After deliberation of the evidence the jury will present their conclusions. On a Jury trial they are the only evaluators of the evidence and only they can make a decision. Once a Jury decision is made their role in the trial is over.