A more thorough explanation:

A hold order is a note in a prisoner's record that tells prison officials not to release the prisoner because another jurisdiction has charges against them. Instead, the officials are instructed to alert the authorities in that other jurisdiction.

John is serving time in a prison in California. However, he also has charges pending against him in Nevada. If John's file has a hold order, the prison officials will not release him when his sentence is up. Instead, they will notify the authorities in Nevada so that John can be transferred to face the charges there.

Another example is if a prisoner is wanted in another state for a crime they committed before they were arrested in their current state. The hold order would prevent them from being released and instead, they would be transferred to the state where they are wanted to face the charges.

These examples illustrate how a hold order works to ensure that prisoners face all charges against them and are not released prematurely.