There's a demo on Steam, if you can play it it's better than having it described to you.
If not... well, ok. You don't click on where to go, you control with WASD as if it were a shooter, or hold the right mouse button in the direction you want to go. And the left mouse button is for attacking, period. Not clicking a target to attack or anything, just you will swing your sword/staff if you click it. I didn't get far enough to see how well this even worked, but I have little doubt it would not have been a pleasant experience compared to the controller.
Actually, it's pretty damn telling that if you have a 360 controller plugged in the game will display the Xbox buttons in the menus and completely ignore the keyboard and mouse once you actually start the game proper. With no option to toggle in the menus.