An ACE is a way for developers to create a component by simply focusing on their own data model/provider and simply rely to the Adaptive Card schema for lightweight uniform rendering.
ACEs can be used to extend the EE Dashboard scenario beyond just static functionality. But they can also be used in other M365 workloads as Teams tabs or Web Parts
This package is part of the SharePoint Framework, which is a collection of NPM packages that empower developers to create client-side experiences for Microsoft SharePoint. For more information, including complete API documentation and code samples, please visit the SharePoint Framework web site.