Cloud services means all the services offered by cloud provides.

SaaS (Software as a service)

SaaS is a software architecture that is used by all customers. Basically SaaS is a software that consumed by end user by using an interface.

Example: Microsoft Office 365

IaaS (Infrastructure as a service)

IaaS is widely used cloud service that provides flexibility to create servers, virtual machine, storage and operating systems where you host/runs your application. You have pay whatever you use instead of buying hardware and software. IaaS is used by System Administrator

Example: Azure VM(Linux/Windows)

PaaS (Platform as a service)

PaaS provides an environment to building, deploying and testing the applications. In PaaS, cloud providers provides a platform to use their services like Azure SQL Database. PaaS consumed by technical person like developers, DBA.

Example: Azure SQL Database