The Subtle Joy of Counting
Everyone agrees that counting -- determining distribution and the location of high cards -- is hard work and improves your bridge game.
It also adds a different aspect to bridge, one that can be enjoyable. There are principles of card play that determine what cards you play and what suits you lead in the early play of the hand.
But, if you actively infer distribution and the location of the high cards, the principles go out the window, and you can instead play your cards "double-dummy", choosing the card to play that works the best. There is something inherently satisfying in counting out the hand and discovering the best play to make, especially when it is different from what you would have done had you not counted.
When your head is above water, you get one view of the ocean; when you put your head in the water, you get a completely different view. Counting and inference give you the completely different view.
In these problems, there is one right play. You can find the right play if you count the hand and take all of the available inferences.
The introduction is an introduction to counting, including the basic mechanisms of counting distribution. (Ironically, you should be neither adding or counting when you determine distribution.) The introductory hand runs through a hand for you to count.