What do film distributors do?

My definition: A film distributor is a company or single person responsible for releasing films to the public either theatrically or for home viewing. A distributor may do this directly (if the distributor owns the theaters or film distribution networks) or through theatrical exhibitors and other sub-distributors.
Internet definition: Film distribution involves launching and sustaining films in the marketplace. Because the film business is product driven, Film Distributors must connect each film they release with the widest possible audience. As every new title is distinctive and different, Distributors must be strategic and knowledgeable about promotion and publicity in order to entice audiences to see their films, utilising successful film release plans, created in collaboration with film production and/or studio company personnel, marketing teams, publicity departments and exhibitors
What film distributors have to do?
Ideally, a film's distribution plan is taken into consideration during the scripting stage. The more Distributors know about a production, the more informed are their choices when deciding how to publicise the film, and about its marketing campaign, release strategy, promotional tie-ins, etc. However, in the independent sector, Distributors often become involved only after films premiere at film markets or festivals such as Sundance, Cannes or the American Film Market. Film Sales Agents represent such films when they are seeking distribution, and broker deals between filmmakers and Distributors.
In general, the more money Film Distributors spend on a release, the more interest is generated, which should also heighten what every Distributor wants from the public - publicity by word of mouth. Distributors position films, making the decisions when and where to release a new film, this is decided through a combination of market knowledge, experience and judgment to gauge the target audience for each film. Roughly 350 feature films are launched each year in the UK, and most don't make any money during their theatrical runs. P&A represent the largest expenditure items for Distributors, often amounting to the equivalent of between a third and half of the film's original production budget. Risks are high. A film's opening weekend revenue often brings in as much as 25-30% of its entire box office earnings, and is vitally important to its long-term fiscal profitability and sustainability.
The Film Distributor's Association is the trade body that represents UK Theatrical Film Distributors. It seeks to promote cinema going in preference to other leisure activities. It is also involved with such important issues as anti-piracy laws, stopping the production and sale of fake DVDs.