A PivotTable groups source records and calculates summaries without changing the source. Select a cell in the data, choose Insert > PivotTable, and check the Table/Range. You can put the report on a new worksheet or choose a destination on an existing one.
The PivotTable Fields pane has a field list above four areas. Put categories in Rows or Columns, numeric measures in Values, and report-wide choices in Filters. Checkboxes add fields to a default area; dragging or a field's menu lets you choose another one.
A PivotTable starts with Compact layout and grand totals. It uses a snapshot of its source, called the cache. Changing a sale doesn't change the report until you choose Refresh. A source range that misses the final row also misses that row's contribution.