SaaS: provides software solutions for specific needs and is accessed over the internet. No infrastructure or platform setup is required, as everything is managed by the provider. Depending on the application, you can customize the software to suit your needs.
Examples include: Salesforce, Microsoft Teams, Google Workspace.
PaaS: Allows you to build, deploy and host applications with out managing the underlying infrastructure.
Example, Heroku, Google app engine etc..
IAAS: Provides Virtuallized computing resources Such as ; Storages, servers and networking over the internet.
Examples are; Microsoft Azure, Google Cloud and AWS.