You may want to read up on basic terms for D&D. Thus game relies heavily on that jargon to describe game mechanics.

For example AC is Armor Class and the value defines how difficult you are to hit. Not to be confused with Air Conditioning or Assasins Creed.

As with D&D there are no set-in-stone archetypes. A fighter can focus on throwing rocks to be ranged or a sorcerer can do their damndest to be a melee player. Classes and races do have innate traits that lend themselves better to other roles and synergies.