An airplane can only fly forward, but it does need to change direction and altitude. For that we have control surfaces. These allow us to change the Pitch, Roll and Yaw movements of the plane, so that we can eventually change the altitude and direction.
The pitch controls the direction of the plane's nose. When the nose is directed to a higher position along with a thrust increase, the airplane will ascent. This is called climbing.
A constant roll create a bank – since the lift force is no longer pointing directly up, part of it create a force that pull the airplane to the side. This will make the airplane change its direction continuously.
A change in the direction can also be done with a Yaw. A yaw is a constant change in the nose direction without rolling. This is the way we control the direction of the paper airplane with the PowerUp 3.o kit.