Give me a difference between al-Subh and Al-Fajr.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. The Fajr prayer is the same as " Subh/Morning Prayer", which is one of the five obligatory prayers Allah ordained for His slaves. It consists of two Rak'ahs (units) and is performed out loudly. Its time begins with the advent of dawn and ends with sunrise. There is no difference between the two words, for they are two names for the same thing. Imam Ash-Shafi'e , in "the Um" says: The morning and the dawn are two names for one prayer, and I do not like it to be named except by one of them. At-Tahawi , in "Mushkil Al-Athar", said: It is called 'morning' because it is performed in the time of the morning, and called 'dawn' because it is performed in the time just close to dawn. Yet, many jurists use the term "Fajr" to refer to the supererogatory two-Rak'ah prayer performed prior to the obligatory prayer, and "Subh" to refer to the obligatory prayer. Allah knows best.