https://www.musical-u.com/learn/what-is-the-circle-of-fifths/
The Circle of Fifths (also called the “Cycle of Fifths” or “Circle of Fourths”) is a powerful tool from music theory.
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/