"What is the difference between game development and game design, and what are the common job positions in each?"

Game Development is the act and process of making a video game and it contains many roles that can be filled. Any person on the Development team is part of creating the game in some way, but there are many different areas of expertise within. The bigger the company is, the more specalized each team member can get...on smaller teams you often have to wear many hats.  I'll try to give a brief overview and can elaborate on areas if anyone wants further detail.

Game Designers  A Game Designer generally spends pre-production deciding what kinds of features will work best with the game and creating documents and specs that gives the entire team a clear picture of what everyone needs to work together toward. During production...Game Designers are often building gameplay levels, balancing player and enemy features and working with all the other disciplines to ensure that work created is fitting within the design goals.  The discipline generally breaks into:

• System Designers -  Responsible for the gameplay mechanics like weapons, AI, player abilities, etc.  They generally spend a lot of time in spreadsheets or proprietary tools to balance elements of the game for fun and little frustration.
• Level Designers - Create the gameplay layouts, script the encounters and utilize all the pieces provided by the System Designers to create a cohesive experience for the player.
• Writers - Create the flow of the story and write dialogue for all the vocals in the game.  They usually work with the voice talent to ensure proper line reading.

Audio Design is often considered a subset of Game Design, but their focus is quite a bit different. They have to work closely with the other Designers to figure out not only the audio needed for the gameplay that's expected, but also the mood that has to be achieved. While working on sound effects, voice and music they have a lot of areas to consider and have to be masters at what they do to create an ideal emotional experience that impacts the player.

The Art Team is a very diverse group that focuses on creating compelling visuals while trying to stay within the gameplay parameters set by Design. The best work generally comes when Art and Design are collaborating effectively from the start and have a clear vision together going forward into asset creation.  There are probably a ton of specialties i'm forgetting...but here's the general break down:

• Environment Art & Props - Work closely with Level Designers to create and populate and area that's not only fun but looks great. 
• Characters & Vehicles - Focus on modeling and texturing all of the characters and vehicles for the game.  They have to focus on high quality visuals with strict memory requirements.
• Animation - They create all of the movement sets for the Characters and Vehicles in the game as well as any other objects that require movement in the environment.
• UI - Create the User Interface for the game with all of the HUD elements that the player uses.  Creating something that is visually appealing as well as informational isn't always easy.

The Programming Team is a hugely diverse group of people who are responsible for all the underlying tech that the game is built upon. They provide the engine, rendering, AI functionality, tools for gameplay implementation, complex gameplay encounters, and just about anything else that isn't mentioned above. Programming is a place where you often find people experienced in very particular parts of game programming.

Production is something that varies widely from company to company. At Oddworld we had one producer who was responsible for the schedule of the game creation. At EA, we had many producers who were more in charge of the quality of various areas of the game (missions, outsourcing art, UI, etc) and then added Project Managers who were more responsible for the schedule. I've seen producers take on many hats, but they are always focused on getting the game complete.

Quality Assurance Team or commonly known as QA are the guys who make sure that the rest of the developers did their jobs correctly.  They spend hours upon hours playing the same things over and over making sure that someones recent content or fix didn't break something in the game.  People think it sounds fun to play games all day, but I can assure you...well it is...but it's also a lot of HARD work.  Playing the same 10 minutes of gameplay for 8 hours trying to reproduce a bug that only happens .5% of the time SUCKS.