What is strategy? 

Strategy is the art of being CEO. From ancient etymological greek roots, the word strategy means "art of the troop leader". It concerns how one achieves ones goal under conditions of uncertainty. In business, we do the same. The purpose is to maximize value. And this must be done under conditions of uncertainty and constraints.

To maximize value, we are really talking about long term cash flows. Cash flows have direct drivers. Such as revenues, margins and investments. But over the long run, this reductive approach does not work. Rather, Cash flows are driven by  forces in a complex adaptive system. Competition dominates these drivers. If you have built a very valuable business, and it is easy to replicate, that is what people will do. This competes returns down.

And so, to create value, you must first create a competitive advantage.

Thus, to learn and eventually master strategy, the first step is to understand value. And to understand value, the first we need to understand is the general patterns of competitive advantage.