Global Game Jam describes a game jam like this:

Jam" is a reference to musician jam sessions. The goal is to come together and make a videogame, or non-digital game like a board game or card game. Participants rapidly prototype game designs and hopefully inject new ideas to help grow the game industry. We share a common theme and constraints. We ask participants to create a game from beginning to end in a prescribed time (maximum of 48 hours). The brief time span is meant to help encourage creative thinking to result in small but innovative and experimental games.

Some game jams are much shorter than 48 hours, and can last for example only an hour, while other game jam has a longer time frame of for example 72 hours.

The tight time frame entails several constraints for a design process in a game jam setting. The limited time frame prompts you to come up with game ideas quickly, so that you can start building a game prototype and finish it before the deadline. This means that after getting an idea, all design decisions regarding game play, aesthetics, sound etc. have to be made quickly in order to be implemented into the game prototype and subsequently play tested. During this design process, you might encounter bugs or maybe you find out that the game idea does not work in the way you had imagined, and must come up with an alternative. Therefore, throughout the game jam design process you have to keep the creativity up, so that you are able to come up with alternatives if something unexpected happens with the game idea or prototype, all within a time frame of 48 hours.

Watch this video to learn more about game jams from the perspectives of Rami Ismail, indie game developer and co-founder of game studio Vlambeer, Adriel Wallick, indie game developer and organizer of Train Jam, and Anna Kipnis, senior gameplay programmer at Double Fine:


Interactive

This video stops a certain points to ask you a question related to what you just watched, you can go back in the video if you missed it. Watch the video and see if you can answer all the questions that it asks of you.

GameJam - A Short Documentary (YouTube)