Once the movie is completed, it must be distributed. This is how producers make their money back, hence they invest a lot of time and energy in finding the right distribution deals for their projects. A successful distribution deal involves theatrical release, as opposed to direct-to-video agreement. Naturally, studio-produced movies have distribution from the get-go. Independent producers, in the other hand, often struggle while hunting for the most suitable distributors.
Theatrical distribution is a huge gamble because (1) making several prints of a movie and distributing it nationwide is expensive; and (2) it is unpredictable to tell before how the audience will respond. Like any other art, cinema is subjective. The case of Slumdog Millionaire provides a great example of how a major distribution company doubted the commercial prospects of said movie and passed on it. Eventually, Slumdog Millionaire won eight Academy Awards and grossed hundreds of millions of dollars:
In August 2007, Warner Independent Pictures acquired the North American rights and Pathé the international rights to distribute Slumdog Millionaire theatrically. However, in May 2008, Warner Independent Pictures was shut down, with all of its projects being transferred to Warner Bros., its parent studio. Warner Bros. doubted the commercial prospects of Slumdog Millionaire and suggested that it would go straight to DVD without a U.S. theatrical release. In August 2008, the studio began searching for buyers for various productions, to relieve its overload of end-of-the-year films. Halfway through the month, Warner Bros. entered into a pact with Fox Searchlight Pictures to share distribution of the film, with Fox Searchlight buying 50% of Warner Bros.'s interest in the movie and handling U.S. distribution.
Following the film's success at the 81st Academy Awards, the film topped the worldwide box office (barring North America), grossing $16 million from 34 markets in the week following the Academy Awards. Worldwide, the film has currently grossed over $377 million. (from Wikipedia)