What is an octave in music and how does it impact the overall sound of a musical composition?

An octave in music is a musical interval between two notes that have a frequency ratio of 2:1. This means that one note is double the frequency of the other. Octaves create a sense of harmony and fullness in a musical composition by adding depth and richness to the sound. They are often used to create a sense of resolution and completeness in a piece of music.