Look at this:
What is Arraignment?
Arraignment is a hearing in court in which the defendant is formally charged with an offense, given a copy of the complaint and informed of his or her constitutional rights. The defendant enters a plea of Guilty or Not Guilty at this hearing.
What is a preliminary hearing?
A preliminary hearing is not a trial. It is a hearing in front of the judge in which the prosecutor, the defendant, the defense attorney, and any subpoenaed witnesses present the evidence in the case. The judge will then decide if there is enough evidence in the case to sustain the felony charge. A jury is not present in this hearing the judge alone makes the decision.
What is a Grand Jury?
A grand jury is a type of jury which determines whether there is enough evidence for a trial. A grand jury listens to evidence presented by a prosecutor and investigator and then decides if there is enough probable cause to believe that the accused person actually committed the crime. Prosecutors usually submit a statement of proposed charges known as an “indictment” to the grand jury. The prosecutor then leaves the jurors alone and they decide if the evidence gives them probable cause to believe the accused person(s) named in the indictment are guilty of the charges brought against them. If a majority of the jurors vote for the indictment, it is “returned” and initiates a criminal case against the accused.