Software as a Service (SaaS) provides a complete software solution offered on a pay-per-use basis or as a subscription that users can access and manage over the internet. Users do not have to worry about installation, updates, or maintenance of the software, which is all handled by the service provider. Infrastructure as a Service (IaaS) provides virtualized computing resources over the internet and users must manage or run the software themselves. Platform as a Service (PaaS) delivers a framework for developers to build upon and create custom applications.