https://www.musical-u.com/learn/what-is-the-circle-of-fifths/
What is the Circle of Fifths? It’s a powerful tool from music theory. A way of thinking about the relationship between notes and chords that go together in music.
Learning the Circle of Fifths helps you to more easily play by ear or improvise, by understanding the musical connections between notes and the chords.
https://www.musical-u.com/learn/what-is-the-circle-of-fifths/