Your characters have roles assigned to them and they are as follows:
a) COMMANDO - excels at physical combat
b) RAVAGER - excels at magical combat
c) SENTINEL - draws enemy's attention and acts as a tank
d) SABOTEUR - pesters enemies with negative status effects
e) SYNERGIST - protects the party with positive status effects
f) MEDIC - excels at healing the party and reviving KOed allies
In the lower portion of the screen you have two additions:
a) PARADIGM can be accessed by pressing L1. What does it do? It allows you to change character roles in battle on the fly by choosing one of the predetermined setups (you can have a maximum of six setups).
b) Between the character's name and numerical HP display you'll see a shortened name for a character's role - COM for Commando, RAV for Ravager and so forth. You can assign characters the most effective roles for a given situation by changing your party's paradigms.
You can switch between paradigms as often as you like. Each paradigm assigns specific roles to the members of your party. These roles define the spells and abilities available to a party member, as well as their general behaviour in combat. There's a wide variety of paradigms to choose from. Offensive paradigms concentrate on dealing damage to enemies, while defensive paradigms focus on party protection and healing. It is very important to shift paradigms to suit your situation. You can press the left analog to scan the paradigms available and see the list of roles that each comprises.
For example, the paradigm Relentless Assault is an offensive paradigm in which multiple attackers coordinate their efforts. The paradigm's two Ravagers target whichever enemy the Commando attacks, with the goal of quickly filling the enemy's Chain Gauge in order to stagger it. If you wish to continue using the Relentless Assault paradigm, press Circle to close the paradigm deck. If you wish to change paradigms, select a new paradigm with left analog and then press X.