Do this, and that happens....
At early stages of learning to operate any machine, you use your very modest judgement to figure out what you need it to do, then you use your even more modest skill to control the machine to do it. So you're figuring out what to make your hands and feet do to make the machine move. Two stages. This demands a simple understanding of "do this to make that happen". This is particularly true of aircraft, which are subject to more forces and variables than most machines. That's what instructors are taught to teach you, and you're paying for it, so you may as well listen.
When you reach the stage of hundreds of hours of flying skill, you'll find that you can control the plane with your mind directly, and thinking about what your hands and feet are doing is not necessary. These understanding aids will not be needed anymore, but you're not there yet.
When your instructor demonstrates slow flight, pay particular attention to these characteristics. (Really, landing is slow flight anyway, at its later stages). With the aircraft flying level with full flaps, lots of power, and very little of Pace's very important potential energy, the elevator control will control pitch attitude very nicely, because there'll be no energy to turn into a climb. Power changes will cause the aircraft to climb or descend with surprisingly little pitch attitude change. If you're really neat about doing this, the effects of P factor can be observed too.
When you're flying faster, the effects are more subtle, and likely to be seen to overlap each other. Follow your training......