A more thorough explanation:

A friendly witness is someone who is called to testify on your behalf in court. This person is expected to provide evidence that supports your case and should answer questions truthfully. However, you cannot cross-examine a friendly witness, which means you cannot ask them questions that challenge their testimony or credibility.

For example, if you are on trial for a crime, you may call a friend who witnessed the incident to testify as a friendly witness. This person would answer questions about what they saw and heard, but you would not be allowed to ask them questions that suggest they are lying or mistaken.

If a friendly witness testifies in a way that hurts your case, you can ask the judge to declare them a hostile witness. This means that you can begin to cross-examine them with leading questions, which are questions that suggest the answer you want to hear. However, you can only do this if the judge agrees to the request.

For example, if your friend testifies that they saw you commit the crime, you may ask the judge to declare them a hostile witness. This would allow you to ask leading questions that suggest they may be mistaken or lying.