Each field may contain one or more data bands. Data bands may be ‘real’ indicating that the band data is actually stored in the file or ‘virtual’ indicating the data is obtained on the fly either from a ‘real’ band or from a classification table. In general, each band would have the same data type and all bands would be closely related. For example different frequencies of the electromagnetic spectrum from Landsat satellite data would be stored in multiple bands. Similarly, image data fields would store color in bands for each color (RGB) component.
Note: Most of the raster operations work on the ‘real’ band.