An SSD (Solid State Drive) has many advantages over a traditional rotational hard drive. Seek time is decreased significantly, making SSDs very fast. The drive has no moving parts to malfunction, and does not generate significant heat. It is also lighter than a rotational drive, more power efficient, and completely silent. Finally, the SSD is more durable. If dropped or banged it isn’t as likely to be damaged.
They are not infallible though – always keep a backup!