Reading the circle

Concept

The Circle of Fifths arranges the 12 keys around a clock. Move clockwise and each key is a perfect 5th higher (and adds one sharp): C → G → D → A → E → B → F#. Counter-clockwise drops a 5th (adds a flat): C → F → Bb → Eb → Ab → Db. Neighboring keys differ by only one note — that's why modulating to them sounds smooth.