When applications are delivered as a service, it's called Software as a Service (SaaS). These services are delivered through cloud computing. They can be delivered over an external or "Public Cloud" (the Internet), through a private or internal network, or through a hybrid network which is a combination of both. In a private cloud, an enterprise (company) owns all the resources on-site and shares them between multiple applications. In a public cloud, the enterprise will rent the resources from an off-site cloud provider, and these resources will be shared between multiple tenants. Hybrid is in the middle where an enterprise owns some resources and rents some other resources from a third party.