In Piano and Song: How to Teach, How to Learn, and How to Form a Judgment of Musical Performances, the author Friedrich Wieck, going under the name Dominie, emphasizes the importance of touching keys correctly.
An incorrect touch, Dominie tells his student:
makes too much unnecessary movement, and tries to produce the tone in the air, instead of drawing it out with the keys.
Above all things, I wish you to observe how I try to bring out from the piano the most beautiful possible tone, with a quiet movement of the fingers and a correct position of the hand; without an uneasy jerking of the arm, and with ease, lightness, and sureness.
Although this book was published 144 years ago, it's timely advice for me at this early stage. When I practice, my fingers on the left hand feel unsure. My right hand contorts to play the chords and I rarely get a clean sound. When I see others play the piano, their fingers look relaxed and gently kiss the keys.
I'm working on relaxing though, and "drawing the tone out of the keys". Whatever that means.