What action do you need to take with your transmitter in order to change your altitude?
If you think by moving your elevator stick (pitch control) up or down you aren't alone.
But you would be wrong.
One of the things we learn in aviation - whether it's flying full scale or RC models - is that it's power, not pitch which controls altitude. Pitch (elevator) controls the nose's attitude in relation to the horizon but ultimately it's power which we use when we either want to increase or decrease our altitude.
Let's say you are on the final approach to land. Chances are you are decreasing your power to bleed off airspeed and by doing so it also decreases your altitude. Both things you naturally would want to establish when on the glide slope setting up to land.
You can use your pitch control (elevator) to adjust your nose accordingly in relation to the horizon, and this action is never more crucial than when you settle in ground effect, bleeding off even more airspeed and then using your elevator to flare (raise the nose) so you can enjoy a smooth, safe landing.
Power adjusts altitude and airspeed. Pitch adjusts the plane's attitude in relation to the horizon. Ultimately we want to use both to execute a successful landing.