A fully random game means each new game is completely unique(besides the interface).
Usually accomplished by procedurally generating all aspects of the game: maps, monsters, npcs, quests, items,classes, skills,lore, etc.

A.Characters/Items are compatible between games and can be transferred to new maps/world - i.e. procedural items/classes are independent of the world.
B.Each world allows only classes/factions/items generated by the procedural generation of that world.