When you create a report in Power BI Desktop, the data in that report is stored in a data model.
When you publish a report to the Power BI service, the data model is also published to the service as a dataset at the same time. When you share the report with others, you can give them Build permission for the dataset that the report is built on, so they can discover and reuse it for their own reports, dashboards, etc.
If you have Reshare and Build permission on a dataset, and you share a report or dashboard you built on that dataset, you can specify that the recipients also get Build permission for the dataset.
(Datasets are being renamed to semantic models in Power BI and Fabric.) Reference:
https://learn.microsoft.com/en-us/power-bi/connect-data/service-datasets-build-permissions