What is "The Cloud" and why do I need it?

From Evernote:

What is "The Cloud" and why do I need it?

The Cloud refers to a number of systems and services that are accessible on the Internet. Probably the most commonly used cloud service is webmail. If you have an email account - from just about anyone - you more than likely can view your messages from a web browser on just about any computer or device that connects to the Internet.

As we begin using more and more mobile devices, cloud storage has made it possible to access data from just about anywhere. For example, if you use a photo-sharing service like Flickr  you can upload photos from your desktop, your smart phone and sometimes even your camera. And, as soon as the upload is complete, that photo is available from any of your computers or devices. 

Cloud computing also covers a growing number of useful services that operate online. One very good example is Evernote - the notes management service. If you create or capture a note on one computer/device, it's immediately available to you on any of your devices. Microsoft Office has a subscription service to use their apps online instead of installing them on your computer. When the apps are updated, its all done for you. You don't need to maintain it yourself. Apple uses its iCloud online storage service to seamlessly move files (photos, documents, presentations, etc.) between your desktop, iPhone and iPad. Take a picture on your iPhone and when you get home you'll find it waiting for you on your iPad and your computer.

It does take a bit of setup - connecting your app to the appropriate cloud storage account - but once that's done, your app will take care of the rest. Here are a number of commonly used cloud services:
  • Dropbox - cloud storage. Users get 5GB storage free. Many mobile apps can connect to Dropbox for additional storage. There is also a Dropbox app used to manage the files you have stored there.
  • iCloud - Apple's cloud storage service. It supports synchronizing email, calendars, contacts and other basic information between your devices and desktop as well as providing an online location to backup the contents of your iPhone and iPad.
  • Amazon Cloud Drive - cloud storage. Users get 5GB free.
  • Box  - cloud storage. Users get 5GB free. 
  • Mozy - cloud backup.
  • Carbonite - cloud backup.