You can use the following indexes in methods and callback functions:
Initial Column Index (or Column Index)
Equals the column's index in the columns array.
Visible Column Index
Depends on the column's current location in the DataGrid and changes dynamically when columns are reordered or data is grouped. Use the getVisibleColumnIndex(id) method to get this index.
This index is not equal to the index set in the column.visibleIndex property. The latter is used to reorder columns.
Equals a row's order among rendered rows. This index starts from 0 and increases by 1 per row (includes group and detail rows).