Right now, at this point in the process, our business idea is nothing more than a (hopefully) educated guess. We need to validate that our customers exist, and discover various types of them.
When you're introducing a new product, you can determine which market you're interested in targeting.
There are regular users, who we need to build personas of to get an idea of what their experience will be like using your service.
There are influencer users, who can guide the direction of the product due to having experience with the domain.
In the process of identifying and solving the pains of the user, you need to integrate yourself into their lives so you can validate your hypothesis and clear up any uncertainties about the viability of your product.
You can't just make this up. You need to find a real target user of your application (they should exist if you have a > $1B market) and question them, demo your idea to them and see how they react.
The questions that you ask in the process of evaluating your user should not be yes/no answer questions. And you shouldn't just be talking to the user -- you need to talk to people all throughout the food chain.