An
evaluation function, also known as
heuristic evaluation function or
static evaluation function is used by game-playing programs to estimate the value or goodness of a position. The evaluation function is typically designed to be fast and accuracy is not a concern (therefore heuristic); the function looks only at the current position and does not explore possible moves (therefore static).
One popular strategy for constructing evaluation functions is as a weighted sum of various factors that are thought to influence the value of a position. For instance, an evaluation function for chess might take the form
c1 * material + c2 * mobility + c3 * king safety + c4 * center control + ...