There is a huge difference between an educational game for little kids and an 18+ rated zombie shooter.
Defining the audience is part of the initial creative process. Even if it seems such as a consequence of the kind of game one wants to make, it is important to spend some time thinking about it and having a clear idea of who is going to play the game. The kids/adult example is an easy one, but identifying an audience means asking yourself questions such as who is interested in this game? Which other similar games does he or she play? What are they expecting from a new game in their favorite genre?
Mere demographics are still an important factor in defining an audience, but in our modern world, amazingly, pretty much everyone plays ...
