The "B string" refers to the second string on a standard guitar, tuned to the note B. It is typically the second thinnest string, located just above the G string in standard tuning. The B string plays a crucial role in forming chords and melodies, contributing to the overall sound of the instrument. In addition to guitars, the term "B string" can also apply to other stringed instruments, such as the violin or cello, where it denotes a specific string tuned to the note B. Understanding the B string is essential for musicians to effectively play and compose music.