PaaS: Platform as a Service is a hosted environment for running your server side apps. The environment i.e. the application's runtime and maintenance is managed by the PaaS provider. As a customer of PaaS, you just need to provide your server application binaries and the machine configurations required.
BPaaS: Backend Platform as a Service. This is step ahead of PaaS in the sense that it also contains ready to use server side application modules. As a customer of BPaaS, you only need to write the client side code. This is a solution provided by Shephertz only (unlike PaaS). The ready to use server side application is in fact the same as App42 cloud APIs but hosted entirely for a single customer.
GPaas: Gaming Platform as a Service. This provides a PaaS which is customized for hosting the AppWarp S2 game server. This too is a solution provided by Shephertz only. As a customer of GPaaS, you need to work with AppWarp S2 and then for deployment to test remote setup or production, you can host your AppWarp S2 based game server application on to GPaaS. It has all the requirements of hosting AppWarp S2 application preconfigured and you just have to upload your application code.