Units are Equipment used by the Player primarily to increase defensive stats such as S-Def, R-Def, T-Def, etc., although certain Units do have inherent offensive stats in them. There are four types of Units currently in-game: Rear Unit, Arm Unit, Leg Unit, and Sub Unit. In addition to this, pairing up or having a set of a Unit and/or Weapon Series can give additional stats called Set Bonus.
Player Damage Resistances
There are about four categories of resistance in-game: Striking, Ranged, Technique, and Elemental Resistance, which compromises of the six Elements; Fire, Ice, Wind, Lightning, Light, Dark Resistances. Although, it if common to assume that attacks can be a hybrid, that of which can be Striking and Elemental, the game only takes one type into consideration for the computation in regards to resistances.