How does a chess engine work?

I have Chessmaster 9000. You can set up a position and it will take over for whatever color you want. It always figures out the best possible next move. How does it do this? How does it know which move is higher priority? And how would a programmer tell it to do this? What is the chess engines' strategy?|||A chess engine basically calculates every move in every position (the brute force approach). However it uses a technique called alpha-beta pruning to discard variations that are less optimal so that it's left only with the best moves. Therefore one cannot say a chess engine has a strategy as such, but rather calculates everything in each position. It doesn't think in terms of plans and schemes as humans do. As far as I know everything is valued according to the basic unit value of chess: a pawn. So programmers value a rook at 5 pawns but if it's on the 7th rank give it slightly more: 陆 pawn extra. It must be corrected that chess engines do not always find the best moves in position. It depends on the nature of that position. In very closed strategical battles the computer often struggles to play its best.|||Chessmaster 9000 is a complete chess program not a chess engine. A chess engine is a program which also requires installing into a chess graphic interface such as the free to download Arena. How it is done is way to complex to explain here but it involves mathematics %26amp; advanced programming ability to achieve a result.|||There are many chess engines and they each have their own proprietary algorithms, but In part they work by simply checking thousands of possible moves and possible outcomes. In the early stages of a game they use a "book" of openings."