A. Fear of His torment: Allah promises He will inflict His torment on whosoever used to ascribe partners to Him, worshipping them besides Him, and those who disobey Him and abandon His commands.
B. Fear of Allah: This is the fear felt by learned men and those who know their Lord: " …and Allah warns you of Himself… " (Âl-"Imrân: 28).
When fear settles in the hearts, it eradicates lusts and drives out the love of the worldly life.
The more a Mu"men knows Allah, the more piety and fear he has towards Him. Allah (mighty and majestic is He) says: "Only those fear Allah, from among His servants, who have knowledge" (Fâtir: 28).
This is because when they gained complete knowledge of their Lord and His beautiful Names and Attributes, their piety and fear of Allah increased and poured into their hearts, and it then became apparent in their deeds.
source: islamkingdom