Microsoft SQL Server 2014 Unleashed

Using Datasets

Every meaningful report relies on at least one dataset. In SSRS terms, a dataset is simply an abstraction of some set of source data generated by a query and used within a report. Datasets remember the data structure of the queries whose output they contain (the fields, field names, field data types, collation, case sensitivity, and so on). Datasets also store the underlying query used to derive report data from a data source and are aware of any parameters needed to obtain that data—for example, in cases where the underlying data source is a stored procedure.

Every data-bound control on your report needs a dataset from which it will be populated at report (and query) execution time. In SSDT, datasets are listed in the Report Data ...