This is the core implementation of the Dynamic SQS Listener API. This contains basic implementations that should cover a significant amount of use cases but if it doesn't, the consumer can easily implement their own.
See the core-example for examples of using this core code to listen to a queue in a Java application. If it is a Kotlin application, the core-kotlin-example uses a Core Kotlin DSL for constructing a core message listener.
For more information you can look at the root project README.md which provides more information about the architecture of the application. The API is also a good location to find more information about what each part of the framework is how they interact with each other.