Cloud Service Models
IaaS, PaaS, and SaaS: how much of the stack you manage versus the provider.
Every cloud service sits somewhere on a spectrum: how much do you manage, and how much does the provider manage?
The cloud provides compute, network, and storage. You manage the OS, apps, and data. Example: EC2 virtual machines.
The cloud provides the runtime and scaling. You just deploy your code. Example: AWS Elastic Beanstalk.
Fully managed software. Nothing to install or maintain. Example: Google Workspace, Office 365.
You'll also run into FaaS (Functions as a Service, like AWS Lambda) and DBaaS (Database as a Service, like RDS). Same idea each time: someone else manages more of the stack, in exchange for you giving up some control over it.
IaaS hands you raw infrastructure and you build on top. PaaS hands you a runtime and you just deploy code. SaaS hands you finished software. Moving from IaaS toward SaaS means less to manage, and less control over how it's managed.