PaaS means a Platform as a Service. It is a cloud application platform that is designed for application developers to whom it provides the tools for deploying, running, and managing applications over the entire lifecycle efficiently, from deployment, running, scaling, service delivery (database, message queue, etc.) up to stopping and removing. Cloud application platforms are primarily designed to run cloud applications but, at the same time, they already support traditional web and up to a certain level even legacy applications.
You can give a try to the Home at Cloud PaaS, which is based on the open-source Cloud Foundry Cloud Foundry solution. You can read more abot the PaaS concept in our post describing PaaS or in manual which includes the guide through the PaaS usage.