Hard disk drives consist of a series of metal platters coated with magnetic material. Moving arms with magnetic heads move over the platters, reading and writing data to the platters by changing the magnetization on the film of material to represent binary data bits.
Each platter has a separate actuator arm and two magnetic heads to read and write data to each side of the disk, using organized rings around the platter to indicate tracks. Tracks are then broken down into sectors, speeding up the access to specific data by labeling it with a location on each platter. As the CPU reads data from the hard drive, it's moved across a network run by a control unit, which directs data to and from the processor and other components. Data that needs to be processed quickly is stored in the system's memory, or RAM, as the access speed for the system to communicate with RAM is much faster than that of a hard disk.
Flash memory drives, typically called solid state drives, are newer drives that use integrated circuits instead of disks to permanently store data. Solid state drives have no moving components and provide higher speeds, which decreases the loading speed of software. Both are considered system storage, although due to capacity and price, they have different optimal uses. Solid state drives, due to the increased speeds, are best for operating systems, intensive games and software, while hard disk drives work best for archiving data, such as storing media files.