Chain Combo

Chain Combo is a diffrent way of just using X all the time to attack normaly.

Using chain combo, you combine using X to attack with Z, Creating diffrent combos depending on what order and patterns you click "X" and "Z"

There's also certain chain combo's that require you to be specific levels or above, to be able to use them, all this can be seen by pressing "K" and click on "chain combo" on the middle of the screen"

There you'll also be able to see what buttons you'll have to use in order to obtain each of those combos, some of the combos will give you great benefits in pvP and PvE, they also show good visual effects.

So all in all, chain combo was made to make the early game more action packed for everyone, and ofcourse to evolve attacking patterns into multiple methods of doing it.