A patent holding company (PHC) exists to hold patents on behalf of one or more other companies but does not necessarily manufacture products or supply services based upon the patents held.
Patent holding companies may exist for tax reasons.[1] Patent holding companies may also operate patent pools in order to provide a single source for licensing a patented technology.[2] However, patent holding companies that aggressively seek to enforce patent rights through litigation or threats of litigation are referred to as patent assertion entities (PAEs) or, more pejoratively, patent trolls.[3][4]