This is a glossy term for what used to be called living alone. The notion of living alone is burdened with all sorts of negative vibes. It is mostly conflated with being lonely, but there are a growing number of solo dwellers who maintain that that is a mistake. You can have a large number of friends and an active social life, and yet, when you choose, you can just be on your own and do whatever you want to do whenever you feel like doing it.
It has been pointed out that solo dwelling has been boosted by factors that are perhaps new in our society. First of all, the people who choose to be solo dwellers now have the money to do so in comfort. And then there is the technology that connects us all the time to everyone we know and love, so feeling lonely is not an option any more. But choosing to be a solo dweller is.