In the early stage a startup, which can be a new venture or a new division of an existing company, is searching for a validated business model.
When you start your business the business model is just a set of assumptions, based on your vision as an entrepreneur. An assumption is something you believe in, but haven’t proven it. The reality is that most of the time your assumptions are not true. So you have to question and test your core business assumptions, learn and iterate towards a validated business model.