Cloud SaaS,PaaS,IaaS Microsoft Azure

IaaS – Infaestruture as a Service
Data centre phycal facilty/Bulding
Networking/Security
Servers and storage

PaaS – Platofm as a Service
Operatiing system
Deployment tools, database management, business analytics

SaaS – Service as a Service
Hosted applications/apps

https://azure.microsoft.com/en-gb/overview/what-is-paas/