What is the purpose of generating Reports?

If you want a report to only use certain fields, and particularly if you want it to work with only some records that meet a criteria, it is better to create a query to extract what you want first and base the report on that. You can also include multiple tables and calculated fields in a query easier than trying to do it in a report. It is better to get a query to do the work of extracting fields, records and using criteria than trying to do it in a report. So it is a common thing to create queries for the purpose of extracting the data you want for a report.