XaaS is a collective term said to stand for a number of things including "X as a service," "anything as a service" or "everything as a service." The acronym refers to an increasing number of services that are delivered over the Internet rather than provided locally or on-site. XaaS is the essence of cloud computing.
The most common examples of XaaS are Software as a Service (SaaS), Infrastructure as a Service (IaaS) and Platform as a Service (PaaS). The combined use of these three is sometimes referred to as the SPI model (SaaS, PaaS, IaaS). Other examples of XaaS include storage as a service (SaaS), communications as a service (CaaS), network as a service (NaaS) and monitoring as a service (MaaS).
Following the convention of pronouncing "SaaS" as "sass," "XaaS" is sometimes pronounced as "zass."