How about the IaaS, PaaS, SaaS on Microsoft Azure? What Azure products are IaaS, PaaS, SaaS ?
IaaS: Infrastructure as a Service;
PaaS: Platform as a Service;
SaaS: Software as a Service;
Let me steal an image from the internet to compare above 3 and On-premises more clearly:
(This image is from here)
We can see On-Premises allows us to manage almost all stuff. For example, you own your local computer, you can touch everything on it: Network, Hard driver, OS, Database, Applications, all OS Services.. etc.;
IaaS allows us to touch OS, Database and Applications. On Azure, a Virtual Machine is like an IaaS. We can have it and install an OS on it such as Windows or Linux, we can also install database on it, and any other applications;
PaaS only allows us to touch Applications and Data. On Azure, some services could be in PaaS category such as Azure Service (the concept is similar with Windows Services on Windows, Web Services on Web platform); We can choose application and data as our Azure Service, which relies on other stuff but we do not have to consider and handled by Microsoft Azure; There are also other products on Azure belongs to PaaS such as IoT Hub (Internet of Things Hub);
SaaS seems blocks us to touch anything which we can touch on our local computer usually. The user does not need to maintain anything such as software application, OS, database, network, Services… but just use the software directly. The user even can not realize the software is a software, it is a kind of service. The easiest to understand SaaS on Microsoft Azure platform is Office365, traditional office users can use the Office in web browser directly without installing anything. Microsoft will fix bugs and upgrading any Office products on air without all users’ manual works, everything looks like automatically running – a service.