A group value is an ordered set of values from fields arranged into a group. For instance, the 'Year - Quarter - Month' field group in the image below contains the '1996 - Quarter 3 - September', '1994 - Quarter 3 - August' and '1994 - Quarter 4' group values.
Group values may include values from all fields in the group (like the '1994 - Quarter 3 - August' group value from the example above), or from only some of them (the '1994 - Quarter 4' group value). In the latter instance, the group value has a set of child values. In the Pivot Grid shown on the image below, the '1994 - Quarter 4' group value has the 'October', 'November' and 'December' child values.