Software as a Service (SaaS) is a software delivery model in which a software application is hosted by a third-party provider and made available to customers over the internet. Customers can access the software through a web browser, rather than installing it on their own computers or servers.

SaaS is a popular model for delivering software because it allows users to access a wide range of applications without having to invest in the hardware, infrastructure, and maintenance required to run the software on their own. It also allows users to pay for the software on a subscription basis, rather than purchasing a license upfront.

SaaS is commonly used for applications such as customer relationship management (CRM), enterprise resource planning (ERP), and project management, as well as for a variety of other business, productivity, and collaboration tools. It is also used for consumer-oriented applications such as streaming video and music services, online gaming, and cloud storage.

SaaS is often contrasted with other software delivery models, such as on-premises software and infrastructure as a service (IaaS). SaaS is generally seen as providing a more convenient and flexible alternative to these models, as it requires less upfront investment and allows users to access the software from any location with an internet connection.