What's difference between on-premise and SaaS?
SaaS (Software as a Service), often referred to "on-demand Software", is a model where you're provided with access to the software in the cloud. There's no installation, setup or running of the setup, as the service provider will do this for you. You just have to pay the service provider. Example: Office 365
On-Premise is the "traditional" model where you have to install, setup and run the software at a computer at your physical location. It takes time, personnel and possible equipment. It may also have additional cost to hardware and software. Example: Office 2016


Office 365 is SaaS which provides an online version of the MS Office suite. While Office 2016 is On-Premise Software that will require installation and running.

In addition


PaaS (Platform as a Service) provides a platform which typical includes operation system, databases, web server, containers for executing programming languages. Examples: Windows Azure, Azure SQL, Heroku
IaaS (Infrastructure as a Service), provides as name suggesting infrastructure, like virtual machines, storage, network, network service (firewalls). Examples: Windows Azure, Google Compute Engine