IaaS vs PaaS vs SaaS (who manages what)
PaaS sits between renting infrastructure (IaaS) and consuming a finished app (SaaS). Infrastructure as a Service (IaaS): you manage more of the stack. Platform as a Service (PaaS): you deploy code; platform is managed. Software as a Service (SaaS): you use a finished app. Classify by responsibility, not by 'it's in the cloud'.