A hard disk drive (HDD) is a traditional storage device that uses mechanical platters and a moving read/write head to access data. A solid state drive (SSD) is a newer, faster type of device that stores data on instantly-accessible memory chips.
The hard drive is where all your permanent computer data is stored. Whenever you save a file, photo, or software to your computer, it's stored in your hard drive. Most hard drives have storage space between 250GB and 1TB.