Fusion Drives use an intelligent combination of a small SSD drive and a higher-capacity hard drive. The frequently used stuff gets put on the SSD for quick launching, the stuff that isn’t so speed dependent (like music and photos) gets put on the hard drive. This combination offers large amounts of storage at a low cost. SSDs are more expensive and offer less storage, but are uniformly fast for everything — at least 10 times faster than traditional hard drives.