The different layers of a cloud

Cloud computing is often broken down into three different types of services, generally called service models, as follows:

• Infrastructure as a Service (IaaS): This is the fundamental building block, on top of which everything related to the cloud is built. IaaS is usually a computing resource in a virtualized environment. This offers a combination of processing power, memory, storage, and network. The most common IaaS entities that you will find are Virtual Machines (VMs) and network equipment, such as load balancers or virtual Ethernet interfaces, and storage, such as block devices. This layer is very close to the hardware, and offers the full flexibility that you would get when deploying your software outside of a cloud. If you have any experience with datacenters, it will also apply mostly  to this layer.
• Platform as a Service (PaaS): This layer is where things start to get really interesting with the cloud. When building an application, you will likely need a certain number of common components, such as a data store and a queue. The PaaS layer provides a number of ready-to-use applications, to help you build your own services without worrying about administrating and operating third-party services, such as database servers.
• Software as a Service (SaaS): This layer is the icing on the cake. Similar to the PaaS layer, you get access to managed services, but this time, these services are a complete solution dedicated to certain purposes, such as management or monitoring tools.

We would suggest that you go through the National Institute of Standard and Technology (NIST) Definition of Cloud Computing at https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpublication800-145.pdf and the NIST Cloud Computing Standards Roadmap at https://www.nist.gov/sites/default/files/documents/itl/cloud/NIST_SP-500-291_Version-2_2013_June18_FINAL.pdf. This book covers a fair amount of services of the PaaS and SaaS types. While building an application, relying on these services makes a big difference, in comparison to the more traditional environment outside of the cloud. Another key element to success when deploying or migrating to a new infrastructure is adopting a DevOps mindset.