What is the difference between ISSB and PMA Long course?

ISSB: ISSB stands for Inter Services Selection Board. It is a committee for the selection of commissioned officers in the armed forces of Pakistan, Army, Navy, Air Force and Strategic Plans Division. It was founded in 1952.
Commissioned officers are Second Lieutenant, Lieutenant and Captain. To join Pakistan army as commissioned officer, you must have at least intermediate qualification.

PMA Long Course: PMA Long Course is the backbone of Pakistan army. It is the most comprehensive training program in Pakistan army. Candidates may apply after completing their intermediate (FA/FSc). After successfully completing the long course, candidates have high possibility to go up to the rank of General/Chief of army staff.