What is a platform as a service?

Question

My question is what is a platform as a service, and if my IaaS and SaaS concepts are really true.

IaaS:. When you can specify your needs at the machine level, you consume IaaS, which means that when you can decide whether your application hosted in the cloud will work within 1.7 GHz or 2.5 GHz. Or even how many boxes you need.

SaaS:. When you use software hosted on the Internet at the user level. Therefore, if you use Google Docs using SaaS.

I can’t understand what a platform as a service is. My doubt comes up when I read something like this:

Cloud computing has evolved to include platforms for building and running custom applications, a concept known as “platform as a service” (or PaaS). PaaS applications are also called on-demand, web-based, or software as services (or SaaS). [ http://www.salesforce.com/paas/ ]

Does this mean that PaaS and SaaS are the same? In addition, I can’t understand that PaaS is when you rent, for example, a database in the cloud, say, SQL Azure ... you rent something that is not directly infrastructure or software, but that will help you develop your latest SaaS product. I'm right?

Answer 1

No, this is not the same thing. Suppose you want to implement your own version of SaaS, such as Google Docs. But say that you do not want to provide the hardware and software needed to implement distributed storage, backup, etc. If I provided you with this for a fee, that would be PaaS.

A simplified version of the difference is as follows: the software provides services to its users (spreadsheet, Salesforce management). The platform provides services for software (cloud storage, distributed database, backup). The infrastructure provides services to the platform (memory, local storage, CPU, network).