Types of cloud computing services
Cloud computing services offer convenient, pay-as-you-go models that eliminate costly expenditures and maintenance. Cloud providers host a choice of infrastructure, platform, and software offerings on-site that they "rent," giving your organization the flexibility to turn cloud computing services up and down according to your changing requirements.
Infrastructure-as-a-Service (IaaS)
Think of IaaS as the building blocks for cloud-based IT. In this model, a cloud provider hosts infrastructure components that are traditionally located in on-premises data centers. For example, servers, storage and networking hardware, along with the hypervisor (virtualization layer), usually reside on-premises. With IaaS, your organization can choose when and how you want to administer workloads, without needing to buy, manage, and support the underlying infrastructure. IaaS gets your infrastructure up and running quickly, with a pay-as-you-go model.
Platform-as-a-Service (PaaS)
PaaS builds on the IaaS model, but is usually specific to hardware and software tools for application development. Cloud providers, in addition to providing infrastructure components, also host and manage operating systems and middleware that your developers need to create and run applications. PaaS offers an on-demand, pay-as-you-go model.
Software-as-a-Services (SaaS)
With SaaS, cloud providers host and manage an entire infrastructure, as well as end-user applications. When your company chooses a SaaS model, you do not need to install anything; your users will be able to log in and begin immediately using the cloud provider's application running on their infrastructure. SaaS frees you to think only about how your business will use that software, not how to maintain it. SaaS is available on-demand or by subscription.