When all transmitter sticks are in the center, it's effectively doing PositionHold and will stay in one place both horizontally and vertically.
Leaving the throttle stick in the middle (+-10%) and it stays locked at that altitude (as well as GPS and baro can manage). Hold the throttle stick above the middle to make it climb at a constant rate that depends on throttle stick position. Below half makes it decend. The farther away from center throttle, the faster it moves up or down. Be careful. If you move the throttle stick all the way to the bottom the motors will stop. This is a safety feature to allow you to easily stop the motors when needed. This safety feature can be overridden (not really recommended) with a little bit of high throttle trim. Now you know how to adjust your altitude. I generally set my altitude where I want it and then leave the throttle stick in the middle.
All sticks in the middle and it is in PositionHold. To make it move forward, press and hold the pitch (elevator) stick forward. It will move forward as long as you hold the pitch stick forward. Release the pitch stick and it will slow down and stop. Be careful because it doesn't stop instantly when you release the sticks back to center position. Altitude is managed automatically for you, even in forward flight.
While you are holding the pitch stick forward and it is moving forward, press and hold the yaw stick a little to the left. It will circle left. Holding right yaw will make it circle to the right. As long as you hold the pitch forward you can drive it like a car with yaw. The more yaw, the tighter the turn, just like a car. Too much yaw and you will spin out like a car doing doughnuts.
Instead of using forward pitch stick, you can use any combination of roll and pitch, for instance you can hold left roll stick and it will fly straight left as long as you hold that left roll stick. Now comes the interesting part. While flying (for instance) straight left, the yaw works exactly like when you are flying forward. Left yaw makes it circle left and right yaw makes it circle right. You are driving a car again. You don't need to remember what direction you are moving. Nothing is different than when flying forward.
The doubly interesting part is that you can fly straight left (or right) and use right (or left) yaw to fly a circle with the nose pointed inward the whole time. Great for making a video of something from all sides.
I've been doing this for a while and was talking to a friend about it. I thought I would post as an interesting flight tip. Give it a try. I highly recommend it as your first GPS flight mode. Of course there is a lot to do to get GPS flight working well and you should always have plain Attitude mode available as your takeoff and emergency mode.