SaaS (Software as a Service) is a cloud computing model where software applications are hosted by a third party and made available to customers over the Internet. With SaaS, customers do not install or maintain software themselves but instead access it through a web browser. Key characteristics of SaaS include multi-tenant architecture that allows data and application sharing, easy customization capabilities for individual customers without affecting common infrastructure, and improved access to software from any device with an Internet connection. SaaS is also highly scalable, provides regular automated updates, and offers flexible pay-as-you-go pricing models. It is one of the most common delivery methods for business applications today.