Solid State Drive
For many decades, we have used hard disk drives for data storage. But over time, speeds of processors and memory have advanced so far beyond hard drive performance; today, a perfectly fast computer would be crippled by a slow hard drive. For most purposes, the computer world has moved on to something faster: the solid state drive (SSD).
A hard drive looks very much like a mini LP record player: a spinning magnetic disk stores the data, and an arm moves around to read and write the surfaces of the disk. On the other hand, an SSD has no moving parts. It's all data storage on chips. Today's SSDs are about 100 times faster than hard drives!
Since about 2010, the industry has moved from SSDs being specialty-only, to becoming optional, to becoming standard in all new computers today. An existing computer that has a hard drive can be retrofitted with an SSD for a dramatic boost in performance; or you can replace the whole computer with a much faster one.
Earlier solid state drives did not have very high capacity. They were often used in conjunction with a hard drive, acting as a cache for the slower hard drive in order to speed up performance. Then computers sometimes had two separate drives: a fast but low-capacity SSD for the system, and a slow but high-capacity HDD for extra storage. Today SSDs are inexpensive and high capacity, so a single drive is all you need.
Unfortunately, the push for higher capacity and lower price has made SSDs no more reliable than hard drives. For this reason, a data backup remains critically important. Although they still should be used with the safety net of a backup, they are dramatically faster than hard drives.