A sharp raises a note, while a flat lowers a note.
The Circle of Fifths
In music theory, the circle of fifths (or circle of fourths) is the relationship among the 12 tones of the chromatic scale, their corresponding key signatures, and the associated major and minor keys. More specifically, it is a geometrical representation of relationships among the 12 pitch classes of the chromatic scale in pitch class space.
Introducing the Cycle of 5ths for Alto and Baritone Saxophone - Volume 1
Introducing the Cycle of 5ths for Alto and Baritone Sax - Volume 2
How to Understand and Use: The CIRCLE OF 5THS! -Great for Songwriting and Learning Chords-
8 Facts About the Circle of Fifths that you May Not Already Know