Software-as-a-service (SaaS) is software that's used over a network without downloading it to a local compute environment. The software application is accessed over the internet from a SaaS provider and runs in the provider's predefined compute environment.
How SaaS works
Each user is a tenant in the SaaS provider's multitenant, shared environment. Some customization of the software may be allowed. However, it's uncommon for the user to have much control over the infrastructure compute architecture, location, or service levels provided.