Grouping objects is similar to sorting them, but header and footer sections of a report are available with grouping. For example, a report could group retail sales for each client in alphabetical order and add header and footer information, such as the client name and a sales total.
Group fields are relevant only for reports that have group sections defined for them. Groups can be created in a report before profiles are set up. At first, these group sections apply only to the default profile. When any new profiles are created, each profile inherits the existing groups. You can then change groups for each profile without affecting other profiles, but the groups are always part of a profile.
Group fields affect the order in which objects are returned by the query processor (sort fields within group fields). Once any profiles are created, a group section is printed when the value of a detail item changes. Data is grouped based on the values of database fields.
Your reports can have one or more group header and footer sections.