SOLVED: What is the Difference Between Packaged Software, Software As A Service, Platform as a Service and Infrastructure as a Service

The term ‘Cloud Computing’ is an oversimplified term covering many choices for how to have computers complete a task using on-line resources.  The more specific options explaining the ways to run your computing task in popular use today are:

1. Packaged Software,
2. Infrastructure as a Service (IaaS),
3. Software As A Service (SaaS), and
4. Platform as a Service (PaaS)

These terms simply explain what portions of the IT stack you are contracting out to a web-based solution provider.  At one end is traditional packaged software, in which you are contracting nothing and at the other end of the spectrum in Software As A Service in which you are contracting everything.  This graphic from a Microsoft Azure training event I recently attended provides the most direct explanation of these services I have ever seen: