At our Air Force technical school there was an old Navion, a small single-engine piston aircraft. Besides working on its engine in the hangar, we learned to operate it from the cockpit.
We learned to start the engine from the seat, to read the instruments, height and pressure among them, to work the valves, and to move the control surfaces.
Three surfaces, three axes
An aircraft is steered by moving small hinged surfaces into the airflow. There are three, one for each way it can turn.
The rudder, on the vertical tail, swings the nose left and right. The elevator, on the horizontal tail, points the nose up and down. The ailerons, on the outer edges of the wings, move in opposite directions, one up and one down, and roll the aircraft onto one wing.
Moving them on the ground, you can watch each one from outside and connect it to what it would do in the air. It turns three abstract axes into three things you can see move.
Numbers made of pressure
The instruments were what I found most interesting. Several of the most important numbers in the cockpit are not measured directly at all. They are worked out from air pressure.
We learned about the pitot tube, a small tube facing forward into the airflow. Air rams into it, so the pressure inside is higher than the still air around the aircraft. A separate static port senses that surrounding pressure. The difference between the two depends on how fast the aircraft is moving through the air, and that is what the airspeed indicator shows.
The altimeter works from pressure too: the air gets thinner as you climb, so the static pressure tells you your height. A blocked tube or a blocked port does not stop the needle. It makes the needle confidently wrong.
Sitting in the seat
There were so many things to learn in that cockpit that this is only the part I remember best.
What stayed with me is that an aircraft is a machine you read before you trust. The instruments are measurements, each with its own way of being wrong, and learning the aircraft meant learning where each number comes from.