On an acoustic piano when the player presses a key, it triggers a tiny hammer on the inside of the instrument which in turn strikes a string. The string resonates on the inside of the piano, producing the sound. Pianists will feel a little bit of weight behind the key when the hammer strikes the string and as the pitch gets higher on the instrument, the strings get thinner on the inside. This causes the key to feel a little bit lighter.
Certain keyboards, referred to as digital pianos, feature weighted keys to imitate playing on an acoustic piano. This will help students who are learning and practicing on a digital piano develop proper touch. These keys also tend to be velocity sensitive, which allows students to control volume with their fingers and touch instead of relying solely on the volume knob. Developing a nice touch and sense of dynamics (volume) is an integral skill for any student taking piano lessons in Toronto.