Platform as a Service (PaaS) removes the need for you to manage underlying hardware and operating systems; It allows you to focus on the deployment and management of your applications. It helps to be more efficient as you don’t need to worry about procurement, capacity planning, software maintenance, patching  involved in running your application. 

Infrastructure as a Service (IaaS) contains the basic building parts for cloud IT. It provides access to networking features, computers and data storage space. IaaS gives the highest level of flexibility and management control over your IT resources. It is similar to the traditional IT resources with which many IT departments and developers already know. 

Software as a Service (SaaS) deployment model provides you with a complete product that is run and managed by the service provider. In most cases, people referring to SaaS are referring to end-user applications. With a SaaS offering, you don’t have to think about how a service or  infrastructure is managed. You only need to think about how you manage the application.