Illustrating simultaneous move games:

Games  are  said  to  be  of simultaneous move  if players move without  the knowledge of what the other players have chosen to do. Thus, when  the players take their decisions at the same point  of time  the game is a  simultaneous move game. A  game  is also called  the  simultaneous move when  the  players  chose  their decisions  in isolation, with no  information on what the other player  is doing or will do. For this  reason, simultaneous move  games are  often regarded  as  games  of imperfect information or imperfect knowledge.

Simultaneous move games are most often represented  in normal form using a game table or payoff table. The  table lists the payoffs to all players that will be generated after the strategic interaction among the players. If the  interests of the players are wholly  in opposite direction, any benefit gained  by one player is  loss  to  the other. This type  of  interaction guarantees that  payoff  to  the players will add up to a constant value (often zero). Therefore, these kinds of games are called constant sum game (zero sum game when the payoffs add up to zero). Consider the following example  

In example, the game table shows the payoffs that will accrue to the players land 2, after  the game is played. The player1 has strategies Rland R2 at her disposal whereas player 2 has strategies S1 and S2 at her disposal. The first of the  numbers  in  each  cell  separated by  a  comma represents  the  payoff  to the player  1 and the second number represents the payoff to the player 2. Clearly, it is a zero sum game as  the payoffs  in each cell adds up to zero. Therefore, in this  type  of games  if we  know  the  payoff  of one player we  can deduce  the payoff of the other player. The game Table 2 represents  a shorthand notation of the same game, where only the payoff to the palyerl  is shown. But  there  could be  games  in which players interests  are not  contradictory, as in  zero sum games. These type of games are called constant sum  games. The game table representing these type of games, therefore, must show the payoffs to each player in each cell as in the following example:

Example : Variable Sum Game