One thing that dreams show you is that your psyche is fully equipped to create a world reality, it just needs some basic inputs to work with. In the case of dreams these are memory fragments and kinaesthetic elements from your sleeping body. The same mechanism is employed for waking live and our common world, but now the inputs which appear - in the projection - to come via the senses are such as to build a coherent shared world. What the 'actual' nature of these inputs is is impossible to say, but they do their job as well as they ever need to. This is an understanding based on the nature of the waking world and its ontology, but all of that of course is part of the same construction. It tells you nothing metaphysically, but points to wards certain indelible questions.