Sometimes it’s a lot more complicated than that. Sometimes not.
IMHO:
Basically, the producer’s role can be whatever it agreed upon- it’s the title that counts. It’s also important to note that it differs from feature films to TV.
The classic role of the producer in movies is that he’s the one who got the project made- optioned the book or screenplay, set up the pitches, developed a relationship with the writer, took it to studios, and moved it along through development. Basically, their career success depends on a project actually getting made, which is rarer than may seem. In return, they’ll get a producer’s fee from the studio and an opportunity at profit participation.
But they may have parntered with a financing company to produce it, or two companies may share the development or attachment processes, or a star might require a producer credit to be in the movie. With the credit comes much more weight as far as script changes, creative control, crew assembly, etc.
The people with "producer’ title, and there are usually between 1 and 4 nowadays, are the ones eligible for the Best Picture Oscar. But there are similar titles. On a feature film, the person who actually runs the set of the film- hires below-the-line crew, oversees scheduling, maintains the budget, etc- is the LINE Producer, and in some cases they may get credit in the opening titles as a Co-Producer (different from a coproducer, which means one is a Producer with other names. It can get confusing.)
The EXECUTIVE PRODUCER may be the money guy, a financier, a banker, a welathy investor, a person who owns the company where the funds are coming from, or the person who owns the rights but didn’t get the film set up. Or sometimes the Executive producer is an independent producer with a lot of experience overseeing a picture on a day-to-day basis- a really really good line producer- that the studio may hire, well after script development, to make sure a film goes smoothly.
The Co-Executive Producer can be another money guy, or maybe an important contact that brought major players together, or a manager or packager who played a major part in FINDING the financing for a film.
The Associate Producer is an increasingly throwaway title. Could be bestowed on someone who worked their ass off but is still making his way up and not really a producer yet- or could be given to the executive producer’s buddy, or the author of the original novel, etc.
On a TV show, the Producers usually have the distinction of being writers or creators of the show. The Executive Producer, who may or may not be one of these people, is the person in charge of getting each episode done- the “showrunner” (like a line producer in film.)
Part of the reason for the huge difference is that a film may be indevelopment for years where the only work done on it is transfers of rights, developing script and attracting money, cast, crew and interest. On a television show, the creators pitch it, the network might like it and order a pilot, and from then on- especially if it actually gets picked up- the bulk of the work may be an indefinite period of writing and shooting new product every week.
Now I’ve throughly confused myself- time for someone to come in and correct me…