When deploying to Kubernetes we often talk about applications, but wait … What is an application in the cloud native world? Is it a chart, a git repository, or a bundle of manifests? In the first part of this talk, we’ll highlight some application definition formats and their different approaches. But an application is not _just_ its core business logic. What about supporting services like observability, identity, and data stores - are they part of an app? How are they included in an app? An emerging answer to this is developer platforms and platform engineering. We will show you why platforms are the optimal way to enable this and the first steps on how to build one and integrate it with your apps. In this talk, we’ll give you some insights on building developer platforms to deliver cloud-native applications based on the work of the TAG App Delivery GitOps, Operator and Platform Working Groups, and their whitepapers.