To make it simple enough, each direction has it's own combo, that means 4-5 different combo path, for example O and forward on spear does a full thurst, O and Sides do a slashing attack. each weapon has it's own set, and ill be honest i didn't really go deep enough on each weapon to learn all the combos, there are some videos up on youtube though.
you also have the grid to give you passives and unlock skills like KH (where you can airstep, dodge and things like that , sadly can't give much information here because i don't know that much Japanese).
Aside from that, you can combo your skills with the link skills,for example, have prompto use black hole to magnet all the monsters to one spot and then use thunder or fire spell to take them all out, really efficient and looks cool as well.
so yeah, you got the point.