There are two important things to do in chess: offense and defense

Offense is the art of attacking

Defense is the art of supporting pieces and preventing mate

There are two things to remember in offense: pins and sacrifices

This puzzle below show how strong a pin is. Some people say its a draw but is not because of the pin:

Black's previous move pinned the queen but white's next move is a killer.

                                                                                                                      Sacrifices are very powerful sometimes. You can use it to checkmate your enemy. A puzzle will make you understand:

                                                                                                                                                                                                                                                 This one is good:

Defense is simple. This is an example:

Both of the intend to attack queenside later.

If you need more facts wait for the part 2.