This tool is used to filter or smooth classified satellite images. The tool is part of the MRLC National Land Cover Mapping Tool. Unfortunately, the tool does not currently run in ArcGIS.
The great features in this tool are that it lets the user decide the size of patches to eliminate for each class and it also lets the user decide the classes to use as replacements. For example, if an alfalfa field is next to brushland and there is a small patch of wheat between them, this tool will replace the wheat patch with alfalfa.
Patches are also called: regions, clusters, and raster polygons. The noise or misclassified pixels in satellite images is often called "salt and pepper".