Windows Azure provides many services. Each services has its own usage.Broadly speaking, the services that Windows Azure provide can be separated into two categories, a) IaaS, infrastructure as a service, b) PaaS, platform as a service.
IaaS is basically providing data center hosted virtual machine. Many organizations prefer to use Microsoft Windows Azure hosted VM instead of managing those themselves to simplify the logistics and reduce costs.
PaaS is cloud computing platform technology, for example Blob Storage, Table Storage, Queue, SQL Azure, Service Bus, Media Services, and Mobile services. Each services has its own set of use cases, for example, Blob storage enables Windows Azure application
to read/write/update/delete large binary objects in data center.
Gong Cheng