The Purpose of Short Films

Short Films are created for a number of different reasons, as shown below-

Self Promotion:

This is probably the main reason for why short films are produced. Directors/producers use short films as a way to show their potential to the film industry, and gain recognition for their skills. A lot of mainstream films are actually based on short films made by previously unknown talent. A good example of this would be Neil Blomkamp's "Alive in Joburg", which was a short film about aliens arriving on planet earth, and being treated like dirt by humans. This gained so much recognition that the well known film 'District 9' was based on it.

Another good example of someone using a short film as a form of promotion would be Fede Alvarez. He created a short film called 'Ataque de Panico', on a mere $280 budget. The use of Computer Graphics by Alvarez caught the eye of Hollywood producer Sam Raimi, who offered Alvarez a $300 million contract to produce a Hollywood film.

Educational: 

Short films are also used to educate people on current issues, or warn them of potential threats they may face, and how to react to them/stop them. 'Education for Leisure' would be a good example of this, as this film deals with the issues surrounding parental neglect and the extreme effects this can have on children. Educational short films tend to be government made, and may therefore have a slightly higher budget than expected for normal short films.

Entertainment:

Usually, short films are too long to have too much entertainment value attached to them, and therefore are mostly based around the two themes mentioned above (promotion and education). However, some short films are made for entertainment, and 'The Last Man on Earth', by Carlo Ortu, is a good example of this. This theme is based around a post-apocalyptic genre, but twists at the end to add a jovial effect. Although this film was generally created for entertainment purposes, it was probably used as a form of promotion as well.

In comparison to this, the purpose of feature-length films tends to be for entertainment. This is because producers of high-budget films don't need to worry about things such as self promotion, as they are already an established presence in that field.