PaaS
In plain terms
A cloud model that provides a ready platform to build and run apps.
Going deeper
Platform-as-a-Service gives you runtimes, databases, and deployment tooling so you focus on code, not servers or OS patching. It sits between raw infrastructure (IaaS) and finished software (SaaS).
Under the hood
Trades control for convenience; you can hit platform limits and lock-in, but you avoid OS patching, scaling setup, and much ops overhead.
Examples
Heroku, Google App Engine, Azure App Service, AWS Elastic Beanstalk, Render.
Think of it like...
Like renting a fully-equipped commercial kitchen: you bring the recipes and cook, but the building, ovens, and plumbing are handled for you.