By far the most common reason for playing the games is to experience history. Actually, since simulation games also include many non-historical subjects (fantasy and science fiction, etc.) we might as well face up to the fact that experience of any sort is one of the most important things a simulation game has to offer. This experience consists of the gamer being able to massage information in order to see what different shapes the information is capable of taking.
The essence of a simulation game is that it allows, within well defined limits, a great deal of variety in an otherwise strictly predetermined. historical event. This is the popular "what if?" element in the games. For example, take the fact that General Custer was at the Little Big Horn in 1876. What if he had, at the last minute, taken along his Gatling guns (primitive machineguns) after all? He could have taken the Gatling guns; thus, this is a reasonable what if. He couldn't have taken any flamethrowers simply because he didn't have them. As a final note in this area note that what makes a fantasy game a fantasy game is that it is a game in which General Custer does go to the Little Big Horn with flamethrowers, and maybe even a death ray gun.
The typical simulation game, whether it be historical or non-historical, contains certain types of information. There are generally four kinds of information: geographical, Order of Battle, situational and dynamic potential.
Chapter 2 - How to Play Wargames