Chess Guide for the Intermediate Player/Tactics for beginners

Value
Value is an approximate number for evaluation and analysis. If you are "up in material", the value will be positive; vice versa.

Let's say the pawn is worth 1 unit. Then, bishops and knights (also known as "minor pieces") are worth 3 units, rooks are worth 5, and queens are worth 9. (They are called "major pieces".) The king, of course, is worth ∞ unit, because if you lose your king, you lose the game.

There are two variations of this value system. One says minor pieces is worth 3½ units, the other is more complicated. We'll see the second one in the "Engine Programming" chapter because it is usually used in chess engines.

Note that units are usually referred to as "points".

Defending
Defending is the simplest tactic. If you place one of your pieces so that it attacks a square occupied by a friendly piece, the former is defending the latter. If your opponent captures the defended piece, you can recapture with the defending piece (see below for a description of an exchange). However, if after a defending piece moves and the king would be exposed, the defending piece would not be able to move.

Exchanging
Exchanging means to capture a defended piece. Because that piece is defended, your piece will (probably) immediately get recaptured by the defender. Exchanging is also known as "trading".

We can use the chess piece values in order to decide to exchange or not. What's the value of the piece that you captured? What about the pieces that he captured? For example, you should NOT use a queen to capture a defended pawn (or "trade a queen for a pawn" because a queen is worth 9 points, but a pawn is only worth 1 point.

Sometimes, exchanging can be complex, because a piece can have multiple defenders and attackers, so after the first attacker is lost, the second attacker can continue. This is called a complex exchange. Calculate carefully before a complex exchange. A way to create complex exchange is to build "batteries", which are the lining up of multiplex long-ranged pieces in a row so they can make breakthrough on the piece it is aiming even though that piece is defended.

Trade Example 1: an "even" trade
Now we are going to look at an even trade which happens in opening. An even trade is a trade where you didn't gain any advantage on values, but also didn't lose any.

Batteries
Batteries are formed when multiple pieces work together (e.g. rook-rook, queen-rook, or bishop-pawn).

A triple battery is formed when the queen and two rooks work together. It can be very dangerous. The queen should be placed behind one or both rooks, as it is the most powerful piece.