The circle of fifths is the circle of the twelfth notes in order as we go clockwise they each go up by a fret. So C five notes up goes up to G which is the next one we see to it's right. G five notes up goes up to E and it goes like that around the circle. If we look at it the other way, counter clockwise, we call that circle of Fourths. It's the same thing, we're still going upwards even though we're going counter clockwise. But the notes are going up the fourth towards the center of it. So there's a few important things about this diagram, number one is that keys move in terms of fourths and fifths very commonly so this is a great way to remember how keys change and what the tendencies are for harmony. You also know as we go clockwise around the circle of fifths, that every key has a sharp as we go down. The same is true with the circle of fourths, that as you go counter clockwise, we add a flat every time. So this can be a great way to practice scales, keys,chord changes and remember the tendencies of the chords and also remember how many flats or how many sharps are in each key. You also see a smaller circle in the center, with the same notes in the same order but they start in a different place. So at twelve noon C, we see that the smallest circle says A. That's because A is a relative minor of C. In other words, A minor has all the same notes as C major. That's why when we practice the A minor scale, we use all the same notes as C major. And that's true for every set of relative major and relative minor keys as you go around the circle on both direction. So that the basis for understanding the circle of fifths.