In this first option, Power BI handles everything. We use the web-based Power Query Online tool for structuring the data. Power BI handles scheduling the data refresh.
The underlying data behind the dataflow is stored in a data lake. However, since it’s fully managed, this data lake is not directly accessible or visible to the customer. As with most cloud-based implementations, the infrastructure is hidden under the covers. This is what is happening if your users are utilizing dataflows currently but you haven’t specified a data lake account in the Power BI admin center.
Melissa gives us a great summary of the three patterns, so read the whole thing.