Concept:
The concept stage is where the initial idea for the game is made, the platform for the game is decided (mostly) and the game is pitched to receive funding and a budget. Concept art is also produced to be used in the pitch

Jobs: Lead designer, Producer, Artists, Marketing (maybe)

Pre-Production:
The concept is further developed here. Storyboards, treatments and plot concepts are produced and refined at this stage. Levels or areas are designed here. Producers would tackle the L+E issues the product may raise.

Jobs: Lead designer, Writers, Artists, Producers

Production:
The production stage is the longest average portion of a games development. Its the section of development where the game goes from design documents, concept art and game engines to a completed shippable (thats a word now) product. It primarily involves the games programming as the game is coded, debugged and features are added by (mostly) designer specification. While the programmers are at work, the designers are thinking up and designing new features that could be added, all the while marketing is interracting with the community through social media and producing adverts to spread news about the game. Other notable features such as sound design, voice acting, motion capture are all mostly done in production too.

Jobs: Lead designer, Lead programmer, Programmers, Design team, Audio designer, QA and marketing, Voice acting, Software engineers, Producer, Artists.

Post Production:

This is the post-launch portion of the game. DLCs are planned and produced and patches are done to iron out bugs or add new features. On games with multiplayer, the servers would be upkept and monitored. Marketing will continue to do their thing: producing new trailers or ads for the game and notable DLC.

Jobs: Lead designer, Programmers, Design team (smaller now), Marketing, Software engineers