A more thorough explanation:

Immunity from prosecution is a legal protection that prevents a person from being charged with a crime for a specific offense or set of offenses. This protection is usually granted by a prosecutor or a court and prohibits the government from using any evidence or testimony obtained from the person who was granted immunity against them in a criminal prosecution.

For example, if a person witnessed a crime but was also involved in the crime, the government may offer them immunity from prosecution to obtain their testimony. This means that the person cannot be charged with the crime they were involved in, but they must testify about what they saw or know about the crime.

It is important to note that there are two types of immunity from prosecution: use and derivative use immunity. Use immunity protects the witness from the use of their own testimony against them, but does not prevent the government from using other evidence obtained from independent sources. Derivative use immunity, on the other hand, provides broader protection by preventing the government from using any evidence or information derived from the witness's testimony against them.

It is also important to note that federal grants of immunity from prosecution do not apply to state law. This means that if a person is granted immunity from federal prosecution, they may still be prosecuted for the same offense under state law.