Salesforce Architecture - 1

This post of mine is based on my understanding from the book "Salesforce Architect's Handbook" by Dipanker Jyoti and James A. Hutcherson.
Ever since I have been coding in Salesforce, I have built and delivered applications, without much knowledge on what goes behind it. I was very curious to understand this aspect. How is my app hosted? Where is it present? What are the layers of the Salesforce Architecture? Who ensures that my data is safe, etc. ? The questions are endless and I'm no where close to the answers yet. But, I'm a little smarter than yesterday. ;)
We have all heard of the various solution development options like:
  1. On Premise
  1. IaaS
  1. PaaS
  1. SaaS
I'm not gonna detail each one for you. For your reference, here's a post that I came across on Hashnode by @Jay. It covers the functional use cases of the Cloud services really well.
So, what does salesforce fall under? Salesforce comes under both PaaS and SaaS. The next obvious question is, of course, "How Both?"
  1. PaaS - On Salesforce, you can build your apps either through the Out of the Box configuration features provided or through Customization. The Salesforce Lightning Platform allows you to build your applications, to be deployed on the cloud.
  1. SaaS - In order to access your Salesforce app, you need not bother about installing or maintaining any software. You can simply access it via internet, freeing you from all the hassle of software or hardware management.
This answers my question "Which cloud service option has Salesforce adopted for the users to build solutions on?"
In my next post, I'll be uncovering some more exciting topics on Salesforce Architecture. Stay tuned.