If you have a company that has a multi-million budget for things like company-branded t-shirts, you might be able to sell to a mass market. As a bootstrapped business, you might need to think a bit smaller. Most successful businesses started in a very well-defined niche. They may have eventually grown into other fields, but when they began, they focussed on a small group of more or less similar customers.
This is the main property of a niche audience: they are homogenous in a specific way. They share certain attributes, they have the same problems, and they all crave for a solution that is custom-made for them. Inside a niche, you can find a problem and build a specific solution that makes a difference.
A niche is often defined by what it contains, but it’s interesting to think about what it doesn’t include. By understanding which issues you need to care about and which ones you don’t, you will be able to filter out the noise that makes more general markets so hard to navigate.
You can focus on creating the most value and provide the most impactful solution to your customer’s problems, as people in a niche will have the same pains and problems.