SaaS, which stands for Software-as-a-Service, is a software licencing model. Under this model, a 3rd party provider gives access to software applications located on the external servers to customers via a web browser on mobile or desktop.
There are Software-as-a-Service apps for human resource management and other fundamental business technologies.
SaaS is one of the 3 primary segments of cloud computing. Other two being IaaS (infrastructure as a service) and PaaS (Platform as a service).