FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. See About FME Rasters.
The Height feature type supports rasters with a single numeric band.
The Clutter feature type supports rasters with a single band that has a String palette.
The Array feature type supports multiple numeric bands. The exact makeup of the bands depends on the array type (see the enterprise_array_type attribute).