- SaaS: SaaS is software as a service. It uses the web to deliver applications. Most of the SaaS applications can be run directly from a web browser without any download. SaaS offers email and collaboration, customer relationship management and healthcare related applications.
Eg: Salesforce, Google Apps, Concur etc.
- PaaS: PaaS is product as a service. PaaS provides computing platforms such as operating system, database, web-server etc.
Eg: Heroku, Apache Stratosphere, Windows Azure etc.
- IaaS: IaaS is infrastructure as a service. IaaS are self-service models for accessing, monitoring and managing remote data center infrastructures.
Eg: Google compute engine, Amazon Web services.
- AWS, EC2, Microsoft Azure and S3 belong to IaaS
- Hadoop doesn't belong to any. It is a distributed computing platform.