At a very high level The Cloud can be broken up into two over lapping but distinct groups denoted by their use cases. I'll refer to the first group as The Consumers Cloud and the second as The Engineers Cloud. My next post in this series will go into more detail about The Consumers Cloud, while my last post will go over The Engineers Cloud.
The commonality between both groups is that The Cloud is a set of servers distributed in multiple regions throughout the world. Having multiple servers is what allows The Cloud to handle a lot of data. Having those servers distributed regionally around the world allows The Cloud to be fast by reducing the distance between you and the data that is stored in The Cloud.
The Infrastructure of The Cloud
Cloud providers like Amazon AWS, Microsoft Azure, Google Cloud Computer, and etc provide a set of services that abstract interacting with their servers so that the software their customers build don't have to worry about the details of each individual machine.
Most Cloud providers take concepts like file storage, complex computation, geographic regionalization, and security and make them scalable with demand. If a service has high demand it can have lots of resources to meet that demand. If the demand is low it can use less resources. This is very different than the data center model which required a fixed number of servers. If you needed to scale your service you had to purchase additional hardware. When your demand was low those extra servers were sitting around idle. One of the goals for Cloud providers is to optimize use. This allows customers to pay for only what they use when they need it and to optimize for their particular usage pattern.
Why you should care about The Cloud
The Cloud is what enables so much of what we've come to rely on in our every day lives. When you purchase music from one of the many streaming services, you're investing in The Cloud. When you watch Netflix or Amazon Prime, you're investing in The Cloud. In fact, you wouldn't have applications like Dropbox, Instagram, Facebook, iTunes, YouTube or etc without The Cloud.