There are three types of cloud computing services:
SaaS: Software as a Service
SaaS is a service for customers. The service provider provides a completed product that is run and maintained by the service provider. Gmail and Office 365 are examples of SaaS. The customer does not have to worry about maintenance. They simply use it. Everything else is handled by the service provider.
PaaS: Platform as a Service
PaaS is a service for developers. Developer need specifically configured infrastructure to be able to develop their software applications. The service provider provides this infrastructure. The customers only need to focus on the development, deployment, and management of their applications. Heroku is an example of PaaS.
IaaS: Infrastructure as a Service
IaaS is service for admins. The cloud provider only provides access to its hardware and basic building blocks of a cloud. The customer gets access to the cloud, networking, compute, and storage. The customer is responsible everything else. Examples of IaaS are Google Cloud, Microsoft Azure, and Amazon Web Services.