Go-to-market strategy is one leg of a triad with Business Strategy and Product Strategy: business strategy sets market and monetization choices, product strategy decides which problems the product org solves, and go-to-market strategy governs how the resulting product actually reaches and is sold to customers.
The three are interrelated but distinct: a change in business strategy (e.g., a monetization or market-entry choice) cascades into go-to-market execution and creates the OKR/KPI targets that product strategy is then built to hit.
Apply: When defining product strategy, trace explicitly how it serves the company's business strategy and how the resulting product will, in turn, need a go-to-market strategy to reach customers — don't treat the three as interchangeable.