What is the use of Summary report in Salesforce?

Summary Report:

• It is similar to tabular reports, but also allow users to group rows of data, view subtotals, and create charts.
• It can be used as the source report for dashboard components.
• It is also used for a report to show subtotals based on the value of a particular field or when you want to create a hierarchical list.

The summary report is very much similar to the Tabular report but allowing users to group rows of data, create charts, and view subtotals etc. When you want to know the sum, average, highest, or lowest value of a numeric column (like Amount, Age, or Probability), summarize the column. Summaries calculate subtotals for every group in a report, as well as a grand total for all report data.