The cloud is where the Internet is used to store data and programs are run.
Traditionally in IT we have kept our data on our computer or possibly on a server that was in our network and located at our premises. WE did the same with our programs. They were stored and run either on our local machine or on the server located at out location.
With the cloud data and programs are no longer kept locally but are kept at some central location through out the world. We no longer have the data at our location.
Storing on the cloud has a number of advantages to it. When you keep the information in the traditional way, the only way to access the data you had to be at your computer. Now with the cloud you can be anywhere in the world and be able to access your data. Also with the cloud they will lease you a minimal amount of storage or processing capabilities and then expand when you need to add space or processing ability it expands as needed (at a cost).
Almost all of us have used our email on the cloud for years. Now companies are moving lots of other data and programs and virtual machines to the cloud.
The major suppliers of clouds are Amazon and Microsoft. Amazon calls theirs AWS (Amazon Web Services) and Microsoft calls theirs Azure although for just storing smaller amounts of data Microsoft also has OneDrive. They have both built a number of large data centers through out the world and are building more. One thing people need to be careful of is to make sure that their dat is backed up by them or continue to backup your self.
For instance my web pages I do are actually stored on the cloud. I still keep a copy of the files on my machine so if anything happened to the cloud server I can re-deploy my pages. Shutterfly is a cloud data location for pictures. I use them and upload all my pictures there but I still have them on my local machine and a backup also.
The cloud offers large potential on growing the Internet and World Wide Web.