Azure cloud service is an offering from Azure and specifically designed for hosting web applications, background processing applications [similar to traditional windows service applications] and Azure IaaS workloads means Virtual Machines. Cloud Service in Azure is a container under which applications run. The web application in cloud service is termed as "Web Role" whereas background processing applications are termed as "Worker Role".
Every cloud service created from Azure provides you a DNS name such as "YourCloudServiceName.cloudapp.net". This DNS name is used for accessing web applications over internet. An Azure subscription can contain any number cloud services and one cloud service can contain any number of roles. Each role can run any number of "Instances (virtual machines)" on which actual application executes.
To develop an application cloud service, roles aware we need Azure SDK. Using Azure SDK one can create cloud service type of project from tools such as Visual Studio (for .net) or Eclipse (for java).
