PaaS

PAAS (Platform as a Service) is a hosting environment typically for a web applications written in scripting languages (python, ruby, node) and usually offers simplified setup and maintenance tools compared to a VPS. They usually cost money and are powered by service specific platforms although many offer limited gratis tiers.

Examples

 * Heroku
 * Google App Engine
 * App Fog

Self-hosted Examples
A number of services have been introduced that allow you to use your own VPS as a platform for automatically deploying software to. These can be great for platform independence or when striving for lower costs.
 * Dokku
 * CapRover