Storage devices are any type of hardware that is capable of storing and retrieving data. Most often these devices come in the form of hard drives or optical discs.
There are two main categories of storage devices. Primary storage, such as RAM, is used by computer systems to temporarily store and retrieve data. Secondary storage devices, such as hard drives, offer a more permanent solution. Some electronic devices use flash memory cards as storage devices as well. Generally storage devices can be removed from the computer or gadget and kept separately for backup purposes. USB flash drives are a prime example of this mobility.