There are few steps needs to be done before creating the actual game, which is to develop the game ideas(brain storm), game concept, game treatment and design script. Basically the game treatment document should be a printed version of the more developed sales pitch you make for your game in the formal meeting you have with the investor or publisher, few terms needs to be explained in game treatment document such as the introduction of the game, story background, hooks, challenges, obstacles, control, rewards, boss fight, outcomes,  etc. In some case game treatment document required the description  of the visual art style of the game, sound effect might appears in the game, atmosphere,design concept and target audience. If the document is good enough to get someone interested in the idea, you will get the chance to talk more about it at a meeting.

To me, the high concept works as bigger document that makes you expand the idea on which you are already working, and already turned into a high concept. Some people thinks(I used to think) that as long as you modelling what’s in your head in the computer, there is no point drawing a high quality concept art work. However, without a process of developing the concept design into high quality concept works, it is impossible to eventually come up with a satisfying version and a feeling of your game.

In terms of format, the officially game treatment is a 10-20 pages’ document, attractively produced, enriched with many, good quality pictures, concept art works and everything relative to the game.