Difference between model, resource model, collection and repository in Magento 2

In Magento 2, there are several components that are used to work with data in the system, including models, resource models, collections, and repositories. Here is a brief summary of the differences between these components:

1. Model: A model is a PHP class that represents a single entity in the system. Models contain business logic and validation rules, and are responsible for performing CRUD (Create, Read, Update, Delete) operations on the entity. Models are typically used to represent data objects that are specific to the domain of the application.
2. Resource Model: A resource model is a PHP class that provides a standardized way to interact with the database for a specific entity. Resource models contain methods for reading and writing data to the database, and are responsible for enforcing data integrity rules, such as validating data before it is saved. Resource models are typically used to abstract away the details of how data is stored and retrieved from the database.
3. Collection: A collection is a PHP class that represents a set of entities of the same type. Collections are used to query and manipulate multiple entities at once, and contain methods for filtering, sorting, and paginating the data. Collections are typically used to represent data sets that need to be displayed or processed together, such as a list of products.
4. Repository: A repository is a PHP class that provides a standardized way to interact with a specific entity or resource in the system. Repositories contain methods for performing basic CRUD operations on the entity, as well as additional business logic and validation rules. Repositories are typically used to abstract away the details of how data is stored and retrieved, and to provide a consistent interface for working with data across the application.

In summary, models, resource models, collections, and repositories are all components used in Magento 2 to work with data in the system, but they have different responsibilities and are used in different contexts. Models represent individual entities in the system, resource models provide a standardized way to interact with the database, collections represent sets of entities, and repositories provide a consistent interface for working with entities or resources.