It's kinda hard to describe it. It's simple, but at the same time complex. You take a party of 6, your character, and up to 5 different team members. 4 in the frontline with your character in the front and 2 in the back. Each character, weapon, and summon is part of a different element, either Fire, Water, Earth, Wind, Light, and Dark. Fire is weak to Water, Water is weak to Earth, Earth is weak to Wind, Wind is weak to Fire, Light is weak to Dark, and Dark is weak to Light. Your stats is all based on your class, a weapon grid, and a summon grid.
It's honestly like really a lot to it and its hard to really describe all of it.