Software as a service (SaaS, typically pronounced [sæs]), sometimes referred to as "software on demand," is software that is deployed over the internet and/or is deployed to run behind a firewall on a local area network or personal computer. With SaaS, a provider licenses an application to customers as a service on demand, through a subscription, in a "pay-as-you-go" model, or increasingly at no charge. SaaS was initially widely deployed for sales force automation and Customer Relationship Management (CRM). Now, it has become commonplace for many business tasks, including computerized billing, invoicing, human resource management, financials, content management, collaboration, document management, and service desk management.
• Network-based access to, and management of, commercially available software
• Activities managed from central locations rather than at each customer's site, enabling customers to access applications remotely via the Web
• Application delivery typically closer to a one-to-many model (single instance, multi-tenant architecture) than to a one-to-one model, including architecture, pricing, partnering, and management characteristics
• Centralized feature updating, which obviates the need for end-users to download patches and upgrades.
• Frequent integration into a larger network of communicating software—either as part of a mashup or a plug-in to a platform as a service
