Musical intervals are a way of measuring the distance between two notes.
The list of intervals are...
There are other ways to measure the distance of two notes, you can use "whole steps" and
"half-steps". A step means you go up, or down two notes and a half-step means you go up or down one note. So if you went up from a G note to a C (5 notes/perfect 4th) you would be going up 2 whole steps and a half step.
The list of all notes on the musical scale using sharps are A, A#, B, C, C#, D, D#, E, F, F#, G and G#. The list using flats are A, Bb, B, C, Db, D, Eb, E, F, Gb, G and Ab.