Datasets
A dataset is something that you import or connect to. Power BI let's you connect to all sorts of datasets and bring all of it together in one place.
In the navigation bar, the datasets you've connected to are listed under the Datasets heading. Each listed dataset represents a single source of data, for example, an Excel workbook on OneDrive, or an on-premises SSAS tabular dataset, or a Salesforce dataset. There are many different data sources supported, and we’re adding new ones all the time. See the list of dataset types that can be used with Power BI.
ONE dataset... - can be used over and over. - can be used in many different reports. - Visualizations from that one dataset can display on many different dashboards.