What are the similarities and differences between special intelligence and intelligence officers?

Special Intelligence: a non-professional investigative force used in criminal or national security investigations, which can reflect some of the information needed for investigators in a timely manner, as well as the internal information of the offenders, in order to facilitate the investigation of investigators to solve the case. Special agents are generally volunteers who utilize their backgrounds, connections, identities and skills to carry out assigned tasks, somewhat similar to the "informants" of RTHK. And the name of the intelligence officer is more extensive, some refer to the management of intelligence information, some refer to intelligence collectors.