SAP Query: Purpose of User Group?

Dear Experts,

I have created a small report with SAP query, and it is running successfully. But when try to view this report with another SAP user id, this report is not viewed in SQ01. I have assigned only my own id in user group. I could not underwstand why we give user id there.

Could you please explain the ussage of maintaining user group and other logic of this. only those user are authorized to use who are maintained in SAP Query user group?

Best Regards