Cloud Computing??

Cloud computing is based on pay as you go model. Means you pay what you use. Before cloud computing you buy a server with some specs but if you need to increase any resource of server you do a lot of work (buy resource, integrate in environment etc), but cloud computing do a miracle now you only send an email to cloud providing company or make a call to increase your resources and you will only pay, all the other headache is for cloud providing company. Cloud computing is listed top computer filed in 2015.

In simple cloud computing is "all the processing work is done on remote server rather then on local machine". So, you can focus on project more then the infrastructure and other resources. It has many services. Some of them are listed bellow
IaaS (Infrastructure as a service)
PaaS (Platform as a service)
SaaS (Software as a service) mostly used by almost all types of people. e.g gmail
DaaS (Database as a service)
NaaS (Network as a service)
and many many more

Most commonly we use SaaS i.e email services we use is an example of SaaS. Email service is a software running on remote server.