Cloud Computing ­ simply means the ability to access files and applications online through multiple devices, your computer, browser, or phone.

Cloud computing can also be defined as the ability of your technology to take on the shape you need for the type of project you need to accomplish.

Personnel factors:
The best news about cloud computing for you as an end user is the added flexibility the services offer you, without additional investment in either hardware or software. You can simply use your web browser—which is open anyway, right?—to get to the files you need to work with, make any changes, and save and share the files as you see fit.
For Example:
Put together a project team thru cloud, so that team members all over the globe can collaborate and communicate easily.

Commercial factors:
The great thing about cloud computing for companies is that it enables them to expand the services they offer both staff and customers without ­adding to their own hardware infrastructure. Web services enable companies to connect workers and make collaboration possible on a global scale without adding servers, setting up datacenters, and more. The environment is secure, ­flexible, and expandable to accommodate as many users as businesses need to ­support.
For Example:
Create a meeting space for your regional sales reps by creating a team site for everyone in the cloud, using web servers and software, and you can enable every person to log in from any point they have access to the web.

Cloud computing - Key Characteristics:

• Agility improves with users' ability to re-provision technological infrastructure resources.
• Application programming interface (API) accessibility to software that enables machines to interact with cloud software in the same way the user interface facilitates interaction between humans and computers. Cloud computing systems typically use REST-based APIs.
• Cost is claimed to be reduced and in a public cloud delivery model capital expenditure is converted to operational expenditure. This is purported to lower barriers to entry, as infrastructure is typically provided by a third-party and does not need to be purchased for one-time or infrequent intensive computing tasks. Pricing on a utility computing basis is fine-grained with usage-based options and fewer IT skills are required for implementation (in-house).
• Device and location independence enable users to access systems using a web browser regardless of their location or what device they are using (e.g., PC, mobile phone). As infrastructure is off-site (typically provided by a third-party) and accessed via the Internet, users can connect from anywhere.
• Multi-tenancy enables sharing of resources and costs across a large pool of users thus allowing for:
• Centralization of infrastructure in locations with lower costs (such as real estate, electricity, etc.)
• Peak-load capacity increases (users need not engineer for highest possible load-levels)
• Utilization and efficiency improvements for systems that are often only 10–20% utilized.
• Reliability is improved if multiple redundant sites are used, which makes well-designed cloud computing suitable for business continuity and disaster recovery.
• Scalability and Elasticity via dynamic ("on-demand") provisioning of resources on a fine-grained, self-service basis near real-time, without users having to engineer for peak loads.
• Performance is monitored, and consistent and loosely coupled architectures are constructed using web services as the system interface.
• Security could improve due to centralization of data, increased security-focused resources, etc., but concerns can persist about loss of control over certain sensitive data, and the lack of security for stored kernels. Security is often as good as or better than under traditional systems, in part because providers are able to devote resources to solving security issues that many customers cannot afford. However, the complexity of security is greatly increased when data is distributed over a wider area or greater number of devices and in multi-tenant systems that are being shared by unrelated users. In addition, user access to security audit logs may be difficult or impossible. Private cloud installations are in part motivated by users' desire to retain control over the infrastructure and avoid losing control of information security.
• Maintenance of cloud computing applications is easier, because they do not need to be installed on each user's computer.