First, a joke: News $ Once upon time there was a student selling newspaper. He was good at math, so he did not need a calculator to calculate the change. Instead, he just looked up (at the sky) and did the math in his head. One day there was a piece of cloud in the sky. The guy brought the news paper only saw the student looking at the cloud first, and then said the exactly correct amount of change. He got really surprised, and asked: Cloud Computing!?!?
C loud computing is actually very serious business… What is the cloud computing? Here is an analogy. What if all houses are not wired to the electricity grid, and we all need to supply for our own need in electricity? I will probably have a few batteries at my apartment, to provide electricity. Someone else may get a power generator at home, for same purpose. Everyone will need to keep and to maintain their own electricity sources.
But one day, the houses/apartments are wired to the electricity grid. I (and everyone else) can now just use electricity, and pay by the amount used. There will be no more cost and trouble for purchasing and maintaining their own electricity sources My infrastructure (alone with everyone else’s), the wire, is now maintained by the electricity company.
If we just change the “electricity” to computing needs, and “electricity sources at home” to company server and personal computer, we almost got a whole picture of cloud computing. Many people have computer at home now, with the applications. The hardware and the applications are the resources for computing. When the computer is sitting at home, not being used, this part of computing resources is being wasted.
The “Cloud” is just the electricity grid in the analogy, which consist of many high performance servers (the hardware), and software, specifically designed for cloud services. With cloud computing, instead of having a high- end computer at home to do the computing work, day we may just need a simple client. All this client need to do is to connect to the cloud, and access the resources (CPU time, RAM, storage space, and applications.) The computing and storage are done in the cloud, the client just communicate to the cloud and do the in/out put.
Why is it Cool? The cloud computing is Device and location independent. One can access cloud in different places and different client devices, as long as there is a high speed internet connection. This brings other huge advantages, such as efficiency and reliability. Efficiency: unlike personal computer, the will be less resources left unused in the cloud, as it is shared and distributed between many users. Reliability: As the process and storage are on the cloud, work will not be lost if client devices is damages or lost.
How is it New Cloud computing is different from the traditional Client-server model. In Client-server model, the workload is partitioned between the server and the client computer, and the server and the client computer normally need to be in the same local network. (i.e. Mount Allison Network) In cloud computing, the client may be too simple to do any work other than communicate to the cloud. And it is typically accessed from internet, rather than a local net work.
Examples of Cloud Computing Services targeting personal User Dropbox (With an interesting video at is mainly a cloud storage service, which is an essential part of cloud computing. Once a file is stored in the dropbox, it can be accessed anywhere (even a smart phone) by login from the account. I would rather not embed that video in case something may went wrong.
Google Docs went a step further ahead. Not only the file can be saved on the cloud, it can also be viewed and edited from the web browser, using their web-based interface. (look at my screen shot for view THIS presentation slide in Google Docs!)
Google is already providing a line of cloud services, includes many web-based applications. They even expended this to Android Phones and, especially, their Chrome OS Notebook. The Chrome OS (operation system) is completely browser based, almost everything is accessed from the browser and kept in the cloud. If the Notebook is destroyed, no data on cloud will be lost, again, reliability. An interesting interactive demo here:
There are more cloud computing services targeting institutions and companies, to solve short-term computing needs. The New York Times used the Amazon cloud computing services to process the editions from 1851 to 1922 into digital documents. Such work would take much longer with their own computing resources, since this is an one- time job, New York Times also don’t want to purchase new resources (servers) for it. Cloud computing makes a win-win.
There is also some concern about cloud computing. The Privacy and Security are two of the big worries. People worry about the data and process on the cloud can be watched, lawfully or not. The security issue is also an natural issue of cloud computing. Organizations are formed to discuss the standard in these issues, in order to improve this cool technology. 
Thanks for watching. I hope you enjoyed the likes for demo and video I put in.
References : Distributed Application Architecture". Sun Microsystem. Retrieved : New York Times: Cloud Computing: So You Don’t Have to Stand Still : Cloud Security Alliance Official web page: : Science Squirrels, Cloud Computing: Romance of Cloud of Computers (in Chinese):