There are several kinds of cloud services, depending on which tier of the technology stack the service resides:

Software-as-a-Service (SaaS) delivers entire functioning applications through the cloud. SaaS frees companies from building their own data centers, buying hardware and software licenses, and developing their own programs. Salesforce is an example of a SaaS provider.

Infrastructure-as-a-Service (IaaS) delivers the underlying resources – compute, storage and networking – in a virtual fashion to organizations who purchase service “instances” of varying sizes. In addition, IaaS vendors provide security, monitoring, load balancing, log access, redundancy, backup and replication. Amazon Web Services, Microsoft Azure and Google Compute Platform are all examples of IaaS providers.

Platform-as-a-Service (PaaS) lies in the middle of SaaS and IaaS. It delivers hardware, software tools, and middleware – usually for application development – to users over the Internet. Google App Engine, Red Hat OpenShift, and Microsoft Azure are examples of PaaS providers.

Containers-as-a-Service (CaaS) is the newest cloud service that focuses on managing container-based workloads. A CaaS offers a framework for deploying and managing application and container clusters by delivering container engines, orchestration, and the underlying resources to users. Google Container Engine, Amazon EC2 Container Service, and Azure Container Services are the leading CaaS providers.