A more thorough explanation:

Definition: Use/derivative-use immunity is a type of immunity granted to a person in exchange for their testimony in a criminal case. It means that the person cannot be prosecuted based on the information they provide, or any information that is derived from their testimony.

Example: If a witness is granted use immunity, they can testify about a crime they witnessed without fear of being prosecuted for their own involvement in the crime. However, if the government can prove that they obtained the evidence from a source other than the witness's testimony, they can still use it to prosecute the witness.

This example illustrates how use immunity works in practice. It is a way for the government to compel testimony from a witness without violating their Fifth Amendment right against self-incrimination. By granting use immunity, the government can ensure that the witness is not punished for providing information about a crime, while still being able to use that information to prosecute others involved in the crime.