Definition - What does Informant mean?
An informant is someone who has information about a crime that is going to be committed, or one that has been committed, and tells that information to law enforcement in a covert manner.
The informant would not tell anyone that they passed on the information, and the name of the informer would not be given out by law enforcement.
Justipedia explains Informant
The informant may work on an ongoing basis with law enforcement, or might be induced to become an informant for personal gain: either financial gain or in order to minimize outstanding criminal liability on their own behalf.
An informant could tell something covertly to a business or third party as well (it does not have to be told to specifically law enforcement), but the crux of the subject would be the crime.