Software as a Service (SaaS) is one of the models of cloud computing (next to PaaS - Platform as a Service and IaaS - Infrastructure as a Service), where the application is created and stored on the software provider’s computers, and is available online for the users.
SaaS eliminates the need for installation of the the app on the user’s computer. Furthermore, the SaaS model transfers the installation, administration, and tech support away from the user, to the provider. As a result, the control of the software is in the hands of the provider, who undertakes the role of making sure that it works properly.
Aside from being relieved of the software maintenance, the idea behind SaaS that makes it increasingly popular is that the user purchases a fixed solution, usually in the form of a monthly payment, becoming a fixed cost for the user.
Customers receive the functions and features of the software that they need and simply use it when needed. Users don’t have to buy a license - they only need to pay for using the software when they use it, and can have the access to it whenever it is required.