A market space - much like the real world - is a place where customers and suppliers come together to discuss requirements (from the customer) and the constraints of delivery against those requirements (from the supplier).
Where ever there is a need for a business outcome and the potential for a supplier to deliver a service capable of helping to achieve that business outcome, we have a market space. There can of course be overlaps in market space. This is due to the fact that a service is not simply one component, but a variety of different components whether viewed from the customer perspective (value) or the supplier perspective (service).
At the overlapping points the supplier has an ability to consolidate a variety of operational elements (potentially removing some constraints regarding service delivery).