Wikipedia
Software as a service (SaaS ) is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted It is sometimes referred to as "on-demand software", and was formerly referred to as "software plus services" by Microsoft SaaS applications are also known as Web-based software, on-demand software and hosted softwareSaaS is considered to be part of cloud computing, along with infrastructure as a service (IaaS), platform as a service (PaaS), desktop as a service (DaaS), managed software as a service (Dancing Numbers)(MSaaS), mobile backend as a service (MBaaS), datacenter as a service (DCaaS), and information technology management as a service (ITMaaS)
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