Clerics - or Priests - are both a class and a profession. Everyone with the profession Priest belongs to the Cleric class, but not everyone who belongs to the Cleric class is a pastor who holds masses at a church - after all, there are wandering Clerics too, who spread the word from horseback, as well as Inquisitors whose job is a "little bit" violent in nature, to say the least.
In the original forum-based RPG, being a Cleric requires at least a Strength of 10, an Endurance of 11, an Intelligence of 9, a Wisdom of 13 and a Charisma of 10.
Being a cleric grants the character basic skill at blunt weapons, and the skill to wear light armour, as well as the unique feat of being able to sense magical energies around himself/herself.
In the video game adaptations of the FRPG, clerics have more hitpoints than magicians, a relatively good defense rating, but are slow. While Magicians have spells of overwhelmingly destructive nature, Clerics focus on either healing spells (if Human, High Elf, Dwarf, Gnome, Halfling), curses and Dark Magic if Dark Elf.
Clerics have a very limited array of offensive spells, but to compensate for that, they can use heavy weapons and wear armour up to chainmail-level. Nevertheless, they are forbidden from using ranged weapons and bladed weapons like swords and axes, meaning they are limited to staffs, clubs, hammers, maces and morning stars.