STX debts

Studios who make the film own the rights of a film. Distributors lease (they do not own) a film from the owners (the studio) for a contracted price. When they lease a film they get to use it to make money. They get their money from the theatre owners who pay the distributors to show the film in their cinemas.

There a wonderfully clear description of the whole process here -

entertainment.howstuffworks.com/movie-distribution.htm

EDIT: after reading the link you gave about STX's problems again, I think this might not impact The Mauritanian at all (for now). It seems that the company is selling off its distribution rights to only 48 films in its library in order pay off its debts, and in order to be one of those films (they are unnamed in the article) The Mauritanian would have to had been one of it's big money makers. I don't think it was, right?