SaaS, or Software as a Service, is a model for delivering software applications over the Internet. Instead of purchasing and installing an application on your local computer, you use the SaaS application by accessing it via the Internet.
SaaS tools are typically accessed from a web browser by simply pointing to the application on the company's website. The consumer does not have to install anything other than a simple plugin or extension for their web browser. This allows businesses to easily offer a large number of software products without having to maintain physical copies on their own computers or deploy each product individually onto users' machines.