This layer can be between the domain and the database and provides access to data. They were introduced as part of the Domain-Driven Design in 2004, and want to provide an abstraction of data the application can use, like an interface to a collection.
To know more about to structure the model layer in Laravel check this story on FAT logic to model layer.
They can improve the typical workflow from the domain to the database, adding a layer that centralizes the rules of recovering and data persisting.
This is a base class that holds what is common for all repositories related to Eloquent.