This tag SHOULD NOT BE USED except for questions concerning Esri's ArcGIS platform AS A WHOLE. Product tags (arcgis-desktop, arcgis-server, arcgis-online, etc) combined with version tags (arcgis-10.3, arcgis-10.2, etc) are preferred
The ArcGIS Platform consists of products, versions, applications, license levels and components and their question tagging on GIS Stack Exchange has been discussed at Using tags on ArcGIS questions?
ArcGIS was first released in 1999 and prior to that Esri had a number of different product lines (e.g. ArcView GIS, ArcInfo Workstation, MapObjects, ArcSDE) that were only loosely integrated.