The Cloud is where you are storing information on servers scattered across the Internet you donít own and maintain
The first area many people use of the cloud is storing their pictures and videos on it. Most of these sites are free and let you store a large number of pictures and videos although they limit size of a a picture or video. Places include Shutterfly.com, picasa.com (Google), youtube.com, flicker.com and lots of others. Usually they offer a way to buy prints and specialty items.
The other area that is the fast growing is to store all your other files (data, music, etc.) on the Cloud so you are not limited in accessing them from your PC but can access them from any PC located on the Internet. Many of these charge but a number offer a smaller amount of space for free.
Amazon offers 5gb of storage on the cloud for free and then charges for larger amounts. Theirs is called CloudDrive. Microsoft has SkyDrive which works with their Live group of programs. Microsoft basically gives 25gb of space but can limit number of files uploaded in a month. If you need large amounts of space Microsoft also has Azure where they charge for that.
Box.net also offers various plans for sharing information. Rackspace.com offers space for various prices. I have not used either of these
There are lots of places you can use the Cloud to store information and more places become available regularly. Some people predict we will do all our storage on the Cloud in the future.