The Harrier is in service with the United States Marine Corps (215 aircraft), Italian Navy (18 aircraft) and the Spanish Navy (17 aircraft). Italy and Spain are using the Harrier from their aircraft carriers, the USMC from Amphibian ships, NOT aircraft carriers (standard not, but they can operate from a/c carriers).

United States Marines Corps
The special AV-8 Harrier was developed for the United States Marine Corps (USMC) for attack and destroy of surface targets under day and night in visual environments. The first aircrafts - AV-8A Harriers - came in service with the USMC in 1985. In 1995, the AV-8B Harrier II plus standard was introduced to replace the AV-8A and A-4M aircrafts. .
The harriers are having the VSTOL characteristic to take-off and land vertical. The USMC needed this kind of aircrafts because they: could create a larger tactical mobility, quick response, reduce of operation costs and greater bases flexibility, could operate from sea and from land, are useful for special combats and expeditionary requirements.

Technical