One of the most visible participants during the game, the DM is given the hefty responsibility of overseeing the management of all activities and entertainment involved. While most players are enjoying their play, DMs are busy at work ensuring that all activities run smoothly to keep players entertained and pleased with their stay. DMs are specifically in charge of ensuring all players' welfare and comfort. DMs are responsible for overseeing the social activities for making sure all players are having a great time. DMs must wear many hats, including greeter, event planner, master of ceremonies, customer service manager and cheerleader.
I thought I might also add a job description for a referee. Once again, I've used initials in place of the word "referee."
A DM is the person of authority who is responsible for presiding over the game from a neutral point of view and making on-the-fly decisions that enforce the rules of the sport, including sportsmanship decisions such as ejection.
It also occurred to me that I might include a job description for the Speaker of the House - abbreviated, of course.
The DM's official role is to moderate discussion, make rulings on procedures, announce the results of player decisions. The DM decides who may speak and has the powers to discipline members who break the procedures of the house. The DM often also represents the campaign, speaking of it as "his campaign" in ceremonial and some other situations.
Finally, a job description for what has recently become a populist marketing expert, "chief storyteller":
A DM is able to breathe life into the stories of the campaign's unique message, expanding upon a broad range of subjects from small-game dynamics to benevolent involvement and individual role-playing. The DM's focus is on being highly informed and justifiably opinionated, thinking editorially and developing meaningful relationships both within and outside the campaign. Every player in the campaign is encouraged to act with enterprise and independence.
For me, a DM is a DM. But it scares the hell out of me that a marketing guru is closest of anything to the way I perceive myself running a game.
I don't know what to do with that. Emotionally.