Data storage refers to various methods of saving digital data and preserving it for future use, even when the computer is powered down. All computers include at least one form of long-term data storage device, like a hard drive or solid-state flash drive. They can also store data on external storage devices or other computers called "file servers."
Computer data is stored digitally as a series of bits — 1s and 0s representing an On or Off state. Eight bits make up a byte, the basic measurement unit of data storage. Data is encoded (using different methods for different data types) into individual objects called files. Each file is identified using a filename and given an extension that identifies the file's type. Files on a disk are organized into folders using a file system. Most operating systems create special folders to organize files by source or type, but you can also manage files as you like by creating your own folders.
Computers can store data on a wide variety of storage devices. Solid-state flash memory stores data as a series of electrical charges in memory cells. Hard disk drives store it by magnetizing material on spinning platters. Data can also be stored on optical discs, encoded as a series of pits pressed into the underside of a CD, DVD, or Blu-ray disc. Some computers can write data to special removable magnetic tape cartridges, which are then placed into storage for long-term data archival.
You can also store data on devices other than the computer that created it. USB flash drives and external hard drives are good ways to create copies of files to transfer to another computer. Network-attached storage devices can store files in a way that makes them accessible to multiple computers on a network. Many people also use cloud storage services to keep a copy of their files on a server in a remote data center, allowing them to access their data from any Internet-connected computer.