Cloud Computing basics

SaaS - Software as a Service

is on-demand access to ready-to-use, cloud-hosted application software.

E.g. Google Docs, Google Form, Google Spreadsheet. 

PaaS - Platform as a Service

is on-demand access to a complete, ready-to-use, cloud-hosted platform for developing, running, maintaining, and managing applications.

E.g. Amazon EC2 T2 Micro instances 1 GB memory & 1 vCPU under free tier, Microsoft Azure

IaaS - Infrastructure as a Service

The service provides all of the infrastructures to the business. It provides on-demand access to cloud-hosted physical and virtual servers, storage, and networking - the backend IT infrastructure for running applications and workloads in the cloud.

E.g. host.com that provides dedicated servers to organizations. VMware offers support for IaaS for carving out a system rack, network storage & computer into an isolated system for customers.

StaaS - Storage as a Service

E.g. Carbonite, Amazon S3

Storage as a service (STaaS) is a data storage business model where a provider rents storage resources to a customer through a subscription. STaaS saves you money through operating expenditure (OpEx) agility—you only pay for the storage you need, when you need it.

Private & Public Cloud

Amazon AWS is the poor man's public cloud due to its inexpensive pricing model & is the biggest provider.

HPE/Microsoft are mostly used by Enterprise companies as they hold their server on their enterprise public cloud data center are more responsive to their requests & allow them to perform service testing & site maintenance with escort service. 

GoDaddy - Cheaper public cloud-based hosting solutions though not as customizable as Amazon AWS. 

Critical custom data & sensitive IP, in-house information are kept in a Private cloud & the public-facing web server & catalog information is stored in the Public cloud (e.g. Akamai).

To offer more resilient services load balancing with VM on multiple cloud providers is a hot research topic.