An app is a deployable Component that is consumable in runtime. That includes full applications, as well as, micro-frontends, microservices and serverless functions. A deployable Component contains all the information it needs for it to be built and deployed. Just like any other components, app components are small, and composing other components to fulfill their needs.
An application can be of different types. The most basic type is Node, but different components add new Application Types you can
use for React, Angular apps and more.
Here is an example of two used in this documentation site: