Eight semitones. A soft, slightly sorrowful sound.
Root on string 5, fret 5. Interval on string 5, fret 1.
The minor 6th is used in Romantic and film music to create a sense of longing and yearning. "The Entertainer" by Scott Joplin contains a characteristic minor 6th leap. In classical music, the minor 6th is an element of the "Neapolitan" chord (bII). In jazz, it often appears in altered chords.
Listen to "The Entertainer" and find the minor 6th leap. On guitar, a minor 6th is eight frets on one string. Practice singing the minor 6th, starting from the major 3rd (its inversion). Compare minor and major 6ths by ear.
Learn to recognize intervals by ear with the interactive trainer.