In the long and varied list of producer titles, Executive Producers are at the top of the food chain. In television, they're the tip top of the chain. In film, they're almost at the top, where "Producer" holds the most weight.
In the film world, Executive Producer almost always refers to a hands-off individual who is in some way responsible for the money behind the project. Either they're an executive at the studio, or they discovered the writer/script/idea, or they run or own the production company associated with the film. The exceptions can be when a celebrity is added to give a project credibility, or the EP title is doled out to an individual otherwise un-involved with the financing (see below).
In television, Executive Producers have a slightly different role. Many television EP's are heavily involved in the creative side. Television EP's may be overseeing the entire production daily, or they might be the buck-stopper on the creative decisions. As in most things, the television "rules" are gray-er as to titles.
Because this franchise started on television and then moved to feature films, these Executive Producers are quite a bit more hands-on than your average movie EPs. The one on the left handles the entire budget for the film, as well as all administrative and legal issues. The one on the right has been with the franchise since the very beginning, and he runs all things while shooting. He wrangles talent, keeps things on time, keeps everyone safe, and communicates with the channels who are not present on the road - the studio execs, the post-production team, etc. Both guys have worked with The Gorilla for years and years and they make his job easier.
The Gorilla - he's the cutie in the middle of the top picture - is an example of an Executive Producer who owns the production company (with two partners) that produces a project in conjunction with a studio or network, and he is the creator of the original idea. So he retains the title of Executive Producer for his television projects, but holds a Producer title for his movies. He is also the director.
(Confused yet? I know the nuances appear to have no rhyme or reason.)
Let's recap: In television, the Executive Producer title trumps the Producer title. In film, it's flip flopped, so the Producer title trumps the Executive Producer title. In film, the Executive Producer usually has to do with money. In television, an EP's daily role can vary from the overall boss to the creative boss and anything in-between.
The Executive Producers are always - rare creative decisions aside - listed in the handful of credits that run in the beginning of a movie or television show. They are also listed on the movie poster in the thin fine print. If you were picturing someone in a tailored power suit, you'd mostly be right.
Just not these guys. The only time I've seen them in a suit was at my wedding.