The others have answered this well but I’m not sure they put it all together so I’m going to try. As was said, the tiller is only used on the ground. The reason for this is it has a much greater range of motion the the rudder pedals do and that’s for good reason. On the B717 I fly, the rudder pedals only allow a 17° range for the nosewheel vs the tiller which will give you 82° worth. This obviously allows you to make tighter turns when needed. Maybe not as obvious is you don’t want the rudder to have anywhere near that range as it would surely cause structural damage in flight or a roll over if the nosewheel cranked that hard at takeoff speeds (this is why you don’t touch the tiller until you slow to taxi speed on the ground).
Now in the air the rudders again control yaw (movement around the airplanes vertical axis. Imagine a plane sitting on the ground spinning like a top, that’s yaw). The yoke controls roll (movement around the airplane’s longitudinal axis. One wing comes up, the other goes down, that’s roll). So to answer your question which do you use to turn the plane? The answer is both. If you just used the yoke the plane will turn, however, if you’ve ever seen any of the 827 Fast and Furious movies you know the tighter you make that turn, the more the back of the car wants to “drift” out. It’s the same with the plane. Now while that looks really cool in the movies with cars, we don’t want the back of the plane sliding out on us creating a bunch of drag. We want it to follow the front nicely (like a train). To do that we… you guessed it, need to add some rudder (and get some yaw into the picture). That’s how we make a smooth, “coordinated” and efficient turn. Make sense?
Fyi, the autopilot does this for you.