1. Standard Mandolin: This is the most common type of mandolin and is used in many musical genres, including bluegrass, folk, and country music. It has four pairs of strings tuned in unison, and is usually played with a plectrum.

2. Octave Mandolin: This is a larger version of the standard mandolin and has a deeper, more resonant sound. It is often used in Irish music and other folk genres.

3. Mandola: The mandola is a larger version of the mandolin, and is tuned lower than the standard mandolin. It has a deeper, richer tone and is often used in classical and folk music.

4. Mandocello: The mandocello is the largest member of the mandolin family and is tuned lower than the mandola. It has a deeper, more bass-heavy sound and is often used in classical and folk music.

5. Mandolin-Banjo: This is a hybrid instrument that combines the sound of the mandolin with the body and construction of a banjo. It is often used in bluegrass and folk music.

6. Electric Mandolin: The electric mandolin is a modern variation of the mandolin, and is amplified using pickups and an amplifier. It is often used in rock, jazz, and fusion music.

These are just a few examples of the many different types of mandolin instruments. The mandolin is a versatile instrument that is used in a wide range of musical genres, and its unique sound makes it a popular choice for solo and ensemble playing.