What is IaaS, Paas & SaaS?

These are three main Cloud Computing Stack : Infrastructure as a Service, Platform as a Service and Software as a Service.

• SaaS applications are designed for end-users, accessible over the web.
• PaaS are set of tools and services to help developers design, develop, build & deploy application quickly.
• IaaS serves the need of storage, hardware, servers and networking components.

These cloud computing stacks can provide : 

• any Service on-demand.
• any Platform on-demand.
• large Infrastructure on-demand.

Elasticity of cloud computing brings scalability & accessibility to the applications. 

Examples : Amazon AWS (EC2), Google Cloud (Gmail), Microsoft Azure(Sky Drive) etc.