A more thorough explanation:

A character witness is someone who testifies in court about another person's positive or negative character traits and reputation in the community. This type of testimony is often used in criminal cases, but its usage is limited in civil cases. The testimony must be within the scope of a federal or state rule of evidence.

• In a criminal trial, a defendant may call a character witness to testify about their good reputation in the community or relevant instances of their conduct that demonstrate their character.
• A character witness may also testify about their opinion of the truthfulness and veracity of other witnesses in the trial.

For example, if a defendant is on trial for theft, a character witness may testify that they have known the defendant for many years and have never known them to be dishonest or steal anything. This testimony can help the jury evaluate the defendant's character and whether they are likely to have committed the crime they are accused of.

Similarly, if a witness is testifying in a trial and their credibility is being questioned, a character witness may testify about their opinion of the witness's truthfulness and reputation for honesty in the community.