Fardh and Wajib Salah

The fardh ritual prayers are divided into two groups: the fardh al-ayn prayers that every Muslim who is obliged to perform, such as the five daily salah, and the fardh al-kifayah prayers, such as the funeral prayer, are performed by a few people. 

Wajib ritual prayers are divided into two: wajib by itself and wajib for some external reason.  Ritual prayers that are in and of itself wajib –like the witr- are called li ‘aynihi wajib, necessary by itself. Ritual prayers that are not wajib by itself, but become wajib due to some external cause –like prayers due to an oath or vow- are called li gayrihi wajib, necessary because of an external reason.