CiviCRM Community Forums (archive)

So if you look at "Donor Report (Summary) - Template/Report" for example, In "Display Columns" of "Report Criteria" section, you would notice that there are two sections/groupings in which those checkboxes appear -
One section/grouping of fields consists of contact, email, phone and address fields.
And second of contribution fields.

By default a grouping is created for every table. If we hadn't set 'grouping' in above case, contact, email, phone & address fields would all appear in a separate table.

In "grouping =>  contact-fields", 'contact-fields' is just a label. And all the fields of tables/daos with same grouping label are clubbed together, in a single table layout structure.