What is the difference between a "suspect" and a "person of interest".

Once upon a time, when the cops had a suspect in a crime, the news said that the cops had a suspect. Now, often enough, when the cops have a suspect, the news calls the suspect “a person of interest”.
Most cops I know call them suspects.
Obviously, “person of interest” sounds sort of, well, interesting, like a movie star or a professional athlete. Suspect sounds like, well, somebody suspected of committing a crime.
Which is exactly what they are!
So why the slightly Orwellian reworking of the description by the information media? Why are they trying to make me imagine that a suspect really is not a suspect?