Varieties or errors?

Abstract

When one starts to delve deeper in our hobby, one possible area in which a collector tends to start specialising in is collecting stamps listed as having differences from the normal issue. Amongst the differences which are generally noted on stamps one may find perforations, watermark orientation, re-entries, retouches, broken type, misplaced type, missing colours and different ink shades. All these are generally described, rightly or wrongly, as either varieties (in the majority of cases) or errors; with the most known types being classified under the category of "major" and the less known under that of "minor". [excerpt]