Media Job Position Description

Writer - A writer is someone who is heavily involved in the creation of fictional and non-fictional work.This covers a number of types of media and varied forms including poetry, theatre, screen and radio (such as comedy/soap opera scripts, drama productions and documentaries). Writers may also create the content for websites or write articles for magazines or newspapers.
Generally speaking writers work free lance or you could be so lucky to get a permanent spot at a publication or TV. 

Commissioning Editor - Commissioning editors are essentially the person that decides the content for magazines and book publishing companies. They commission work by finding journalists or responding to book proposals. They are also in control of making sure articles are submitted on time and without grammatical error.
http://targetjobs.co.uk/careers-advice/a-to-z-of-careers/commissioning-editor Producers - Producers are some of the main people involved in making a film. They oversee the project from conception to completion and will sometimes be involved in the marketing or distribution of the film Producers work closely with directors and other production staff on the shoot. It is becoming more regular that they need to have directing skills themselves as the producer may also be the director and may take care of all project operations. Producers arrange funding for each project and are responsible for keeping the production within the allocated budget.http://entertainment.howstuffworks.com/executive-producer1.htm

Script Editor - Because most films are not directed by their scriptwriters, the writer and the director may have different views of the story this link is aided by the script editor. Overall, the director and producer dictate the way the film will be shot, so the writer's original vision must be changed to the vision of those in charge, just like everything else in life. This may mean cutting or combining characters, adding or removing subplots or re-doing scenes for practical reasons such as an to small of a budget to properly reproduce parts of the writer's story. In television, shows that use more than one freelance writer for different episodes require someone with a knowledge of the overall storyline to ensure each episode fits well with the surrounding stories and things dont begin to cross over or move to a nonsensical path.https://careers.bbc.co.uk/fe/tpl_bbc01.asp?newms=jj&id=25369

Agents - Talent agents often receive a basic salary, as well as a commission, or percentage of an income their clients generate. Talent agents who are self-employed often work on only commission, so if the talent fails so does the agent essentially. Depending on the size of their industry and general success, talent agents can sometimes sit back and wait for entertainers to come to them, turning a lot of people away in the process. A talent agent must have an eye for what type of talent the industry needs, then work on selling clients to those who do the hiring, such as movie casting directors, record executives or television news directors.http://www.mymajors.com/careers-and-jobs/Talent-Agent