What do you mean by matrix in SSRS? What are sub-reports and how do we create them?

A matrix is a data area associated with a report set. We may use matrices to make crosstab reports with the report variables shown in rows and columns.

A sub-report is similar to any other report that may be found in the main report and created through it. Parameters can be granted from the main report to the sub-report, and a report can be generated as a result.