Business strategy is the integrated set of choices that determines how a company creates and captures unique value. It includes which markets to serve (and which to exclude), how to position relative to competitors, what to build vs buy vs partner for, how to win in chosen markets, and what trade-offs to accept. The discipline is making explicit choices that produce a differentiated position rather than defaulting to generic "be excellent everywhere" non-strategy that produces no actual competitive advantage. Strategy is choices; without choices, there's no strategy.
What strategy actually is (per Michael Porter and others):
Choices about scope: