This resource type embeds a serverless application from the AWS Serverless Application Repository or from an Amazon S3 bucket as a nested application. Nested applications are deployed as nested stacks, which can contain multiple other resources. For more information about nested applications, see Nested Applications.
The following is an example of a nested application from the AWS Serverless Application Repository:
A serverless application can include one or more nested applications. You can deploy a nested application as a stand-alone artifact or as a component of a larger application.
As serverless architectures grow, common patterns emerge in which the same components are defined in multiple application templates. You can now separate out common patterns as dedicated applications, and then nest them as part of new or existing application templates. With nested applications, you can stay more focused on the business logic that‘s unique to your application.
原文：https://www.cnblogs.com/cloudrivers/p/11617206.html