Anyone who uses computers knows how much storage is important, as storage capacities have increased 
immensely and for a very reasonable price, which means anyone can acquire a large-capacity storage device, for storing his data, for backing up, or for any other purpose.
Computers are based on storage devices, as the programs needs to be stored somewhere to be run from there, mostly it will be a Hard-Disk drive, either internal or an external one.
Which storage types of solutions do we have today ???
- Compact Disc, DVD, DVD/RW – those are writable CDs/DVDs which you can burn files to, and store for a long time, as long as they stay at a cool place.
- Hard-Disk drivers, internal or external – These are the most common storage devices we know since the beginning. They have increased in size and can contain a large amount of data. They can be connected together by a controller, to create a larger continuous storage space, for even larger capacities (RAID controllers). The downfall of such drives is that if they FALL they are most likely become unusable.
- Solid state storage – like USB flash memory units, smart cards, SSD, etc… – which increase in capacity, and will eventually I believe reach a large amount of capacities, hard disk drives do. The reliability is much higher than a hard-disk. If the SSD fails, it doesn’t get damaged and it usually smaller and more easy to carry.
- DAS – direct-attached storage – This means a digital storage system, which is directly attached to a server or workstation, without a network connection (which has the network limitation, in terms of read/write speeds.
- SAN – Storage based on fiber-optic networks, which guarantee a fast connection – This storage solution enables the Gigabyte speed of data traffic between host and destination. Usually used in distant storage locations.
- NAS – Network Attached storage – solution for multiple clients simultaneously, good for data archiving, backup and redundant storage.
After giving some examples, you can see that there is a storage technology for each purpose, some intended for large organizations, some can be used by regular users, even for home backup purposes.
You can find a good comparison table on this link:
http://whatis.techtarget.com/definition/0,,sid9_gci1088267,00.html