Pitch is the term we use to describe how high or low a sound is. Pitch is often synonymous with the terms tone and note. One might say that a person with a high voice sings high pitches, or high notes/tones. A person with a deep voice often sings low pitches, or low notes/tones.
In the United States we label pitches using letters A through G of the alphabet. Counting forward in the alphabet, the pitches get incrementally higher. Once we arrive at the letter G, we begin the musical alphabet at the letter A again. When we have moved through eight letters of this musical alphabet (A-B-C-D-E-F-G-A), in this case from the first A to the next A eight pitches higher, we call this relationship an octave (see below). See the video lecture in the next tab for a more in-depth discussion of why we don't use additional letters, like H, in our musical alphabet.