A show cause order is an order of the court, directing a party to a lawsuit to appear on a certain date to show cause why the judge should not issue a specific order or make a certain finding. It is also called an order to show cause or OSC.
A show cause order is commonly used in a family law case. The hearing of the show cause order is customarilly not an "evidentiary" hearing. An "evidentiary" hearing is where each of the parties is sworn under oath and takes the witness stand to provide testimony (evidence) to prove the facts for the judge's ruling. But normally at the show cause order hearing the parties have provided their evidence in the form of a written declaration signed under penalty of perjury.
In some cases, orders to show cause are filed by a party requesting a court ruling on: child custody, child visitation, child support, spousal support, attorney fees and costs, property restraint, and property control. They are mostly used to modify already-existing orders issued by the court.