Chrome OS features multiple app platforms, such as ARC++ and desktop PWAs, that are based on different underlying technologies. UX-wise, it is an explicit goal to minimise the differences between them and give users the feeling that all apps have as similar properties, management, and features as possible.
This directory contains generic code to facilitate app platforms on Chrome OS communicating with the browser and each other. This layer consists of app-platform-agnostic code, which each app platform's custom implementation then plugs into. Example features include:
ash/apps/intent_helper - allows installed apps that handle particular URLs to be opened by users from the omnibox. For ARC++, custom code queries the ARC++ container; for desktop PWAs, data is contained in the browser itself.