so, lately I have noticed that many movies have a some kind of a producer and for many of them the executive producer is Stieven Spielberg. So, what's the difference?
The producer actually gets the film made. Executive producers usually provide money or resources but, although they have some say in what happens (it's their money after all), will be less involved in production.
A producer actually does work. He coordinates the efforts of various departments, etc. An executive producer is typically someone who has attached their name to a project to give it more clout, so that it will have an easier time getting financed. They will have some creative input on the project, but in general they are just setting things into motion and letting someone else do the heavy lifting.
Generally, the producer is more hands on with the project, be it music, film, theatre, etc.... He/she is responsible for providing everything that is needed for the project, including in some cases, creative input. The Executive producer is more of a financial backer to the project. Not as hands on, but probably had a big interests in the project, thus, getting it off the ground. In some cases, EP credits are given as "gifts" to big-wigs who were close to the project.
An executive producer is the money man who finds the cash to make the movie. The producer or (line producer) is the person who is responsible for the day to day operations and hires the director and crew. The director and producer hire the cast ...