The way distributors work is they each represent certain motion picture studios. They rent you the films, and provide you the all important performance license. Without a license you run the risk of prosecution under copyright law which studios police ardently. The distributors offer a variety of rental options from flat fee to percentage of the gate, to combos of the two just like the studios. These guys are also a lot easier to work with.
Studios require really significant financial guarantees.
The drawback is they have restrictions regards advertising and promotion. These distributors primarily service educational, correctional facilities and organizations other that general theaters. Thus, their contract prohibits newspaper, and radio advertising. These are the big guys. Also, because real theaters deal,in such large amounts of revenue, studios require hefty financial credentials to guarantee their return.