STOVL maybe a domain that PAF will have to look into in future. If not now then maybe 50 years ahead. Harrier was not conceived solely as a naval jet but it was also expected to take off from unprepared landing zones when all the air strips will be taken out by Soviets in Cold war era. This was one of the reasons it was armed with AGM-65 (non navalised version) to destroy enemy armor, bridges etc.
STOVL stands for Short Takeoff Vertical Landing. STOL is Short Takeoff and Landing. VTOL is Vertical takeoff and vertical landing.
STOL and rough field performance is what you need in a decentralized ground basing strategy for fighters / ground attack aircraft.
Regarding why the STOVL requirement was one of the key problem that caused the F-35 problems: https://www.cbc.ca/fifth/blog/extended-interview-pierre-sprey