Software as a Service (SaaS)
The most widely recognized type of cloud service is known as software as a service, or SaaS. This broad category encompasses a variety of services, such as file storage and backup, web-based email and project management tools.
Examples of SaaS cloud service providers include Dropbox, G Suite, Microsoft Office 365, Slack and Citrix Content Collaboration. In each of these applications, users can access, share, store and secure information in “the cloud.”
Infrastructure as a Service (IaaS)
Infrastructure as a service, or IaaS, provides the infrastructure that many cloud service providers need to manage SaaS tools—but don’t want to maintain themselves. It serves as the complete data center framework, eliminating the need for resource-intensive, on-site installations.
Examples of IaaS are Amazon Web Services (AWS), Microsoft Azure and Google Compute Engine. These providers maintain all storage servers and networking hardware, and may also offer load balancing, application firewalls and more. Many well-known SaaS providers run on IaaS platforms.
Platform as a Service (PaaS)
The cloud service model known as platform as a service, or PaaS, serves as a web-based environment where developers can build cloud apps. PaaS provides a database, operating system and programming language that organizations can use to develop cloud-based software, without having to maintain the underlying elements.
Many IaaS vendors, including the examples listed above, also offer PaaS capabilities.