Let's say you are playing a game and you have reached what seems to be a critical position. You sense that the decision made at this move will have a great impact on the result of the game. We will not go into the entire process of calculating a variation at this moment. Let us limit ourselves to stating that before you jump into calculating variations, you should first identify the candidate moves. A candidate move is a move that you think looks interesting to check, and the full list of candidate moves are the moves you think you should have a look at before you decide what move to make on the board. Next, you should take one candidate move at a time and start calculating it. The moves that you think the opponent can answer with are your opponent's candidate moves and they have to be considered too during your calculations. To sum up, a candidate move is a move that you think can be good, and it does not have to be your own move, your opponent's moves will also be candidate moves that you need to check out. If you are interested in how to calculate variations in a position, then we will get back to it many more times! Good luck!