A "difference" operation is a geoprocessing operation that completely removes one overlapping polygon and the intersection of that polygon from the other. It uses one polygon to "take a bite" out of another.

Use this tag for questions relating to geoprocessing operations that involve differences between features.

Do not use this tag for questions comparing the difference between two or more non-geoprocessing things, for example software comparisons (which should be asked at the Software Recommendations Stack Exchange, after reading their help on how to write questions suitable for their site, rather than here anyway)