Who are you building your value proposition for? What "jobs" do they want to get done? What "pains" do they want to solve and what "gains" to they want?
Customers don't exist to buy your product, your product exist for them. You need to understand the details of who these people (your customers) are. This can be achieved with a customer archetype.
This milestone will focus on helping you answer these questions and more about your business as we explore and complete the business model canvas.