In film, producer credits are complex, and their meanings can vary wildly from film to film, or even from producer to producer on the same film. In 2004, John August wrote this blog post, which covers the topic in detail.
In television, where bigger-picture writing is usually done collaboratively in the writers room, the writers are the producers. They guide the show — plot direction, as well as style and presentation. The different producer credits in television in television usually equate to the writers’ levels, or how senior they are.
The one noteworthy common exception in television is the Executive Producer credit. This credit is given to the showrunner, or the head writer, and is sometimes also given to other important members of the production. These could include the show’s creator if different from the showrunner, other high-level writers (often future seasons’ showrunners), the owner/creator of source material, a show’s star, the star or writer or creator’s manager, a high-level executive or creative type (like Steven Spielberg) influential in the show’s creation, or any other number of people.