Column Groups are where columns are 'banded' together with a common header, and each column can only stay inside the Group.
In this demo, 3 sets of column groups have been created: Customer Info, Order, and Shipping Details
All other Modules in AdapTable will 'honour' this column grouping and work appropriately.
For instance if you edit a Layout with Grouped Columns, they will marked as such, and the Editor will not allow them to be dragged out of their parent group.
Likewise the With Special Cols Layout - which includes 2 special columns (Calculated Column and FreeText Column) - displays their position in the Grid as normal.