The Combination

With reasonable defense, not much can be done with one piece only; so most success in chess involves two or more pieces working together. A real combination may well involve captures and perhaps even a sacrifice.

Forced moves, Forcing Moves & Forced Mate

A sequence of moves to which your opponent has no, or very little choice in her replies, typically these are involved in a comination or perhaps lead straight to mate - in which case it is a forced mate. You are playing forced moves when any other move is much less 'playable' than the one you played. Captures are often seen as forcing moves, though even then there may be a choice of "how" you recapture. A check, since your opponent has to answer it on reply, though some checks are less forcing than others.

Major & Minor pieces

The Queen and Rook are said to be the major pieces and the Bishop and Knights minor pieces