A more thorough explanation:

A government agent is a person who works for the government and is authorized to act on behalf of the government. This can include:

• Employees or representatives of a governmental body
• Law enforcement officials, such as police officers or FBI agents
• Informants, especially inmates, hired by law enforcement to obtain incriminating statements from another inmate

For example, a police officer who arrests someone for breaking the law is a government agent. They are authorized to act on behalf of the government to enforce the law and maintain public safety.