While you build and market a product, it is important to decide (at least to start with) if you want to make a product with functional expertise or industry expertise. There is no wrong approach, but at the same time there are trade-offs in both of them. In order to define it, consider an analogy in terms of depth and breadth. How deep you go or the depth you cover, defines how much expertise you are building in your product for a particular industry. How much wide you expand or how much breadth you cover, defines how many industries have application for your product.
Functional expertise is what we can define as a mile wide and an inch deep. A product that is great at doing one particular thing or solving one particular problem and is applicable to solve the same problem in multiple industries. When you go for this approach, the goal is to do one thing, but do it better than anyone else. You should have the core platform that is solid enough to add a different skin and be applicable in another industry. The upside for the approach is that you have scope to expand your reach to multiple industries. Your product can be the standard product of choice for solving that particular problem in any industry that faces the problem. Downside being you are not expert in any one industry and your customer might be more comfortable dealing with a product suite that solves many other problems for them along with the one you are addressing.
Industry expertise is something that can be defined as an inch wide and a mile deep. You develop a product for a particular industry but that product (or family of products) address many issues in one industry. When you go for this approach, the goal is to become integral part of this industry. Your product should be the best there can be to solve the problems in this particular industry. The upside is while you market the product, you are building strong relationship with one particular industry. If you do it right, you build trust with your customer in that particular industry. The downside for the approach is you are dependent on the one particular industry. Your success and failure would have direct correlation with the kind of reception your product receives in this industry.
When you start building the product, you are working at dimensions of an inch wide and an inch deep, or in other words, you are solving one particular problem in one particular industry. The way to expand is to contemplate if you love that particular industry or that particular product. Do you find scope and expertise to do a lot more in that particular industry or do you see application for your product to be applied to multiple industries? It is very lucrative to go for a mile deep and a mile wide, but more often than not, it is wiser to pick an inch in either one of the two dimensions!