What is Object Document Mapper (ODM)?

An Object-Document Mapper (ODM) is a tool that allows you to interact with your MongoDB database using JavaScript objects. It maps your objects in the application to documents in the database.

Usually, when you interact with a MongoDB database, you work directly with the documents in the database, which are stored in a format called BSON (a binary version of JSON). You use MongoDB commands when you want to create, read, update, or delete a document.

An ODM, like Mongoose, provides a way to interact with the documents in the database using JavaScript objects. With Mongoose, you can define a schema (a blueprint) for your objects and then use it to create instances of those objects. These instances can be saved, retrieved, updated and deleted in the database using mongoose methods.

For example, let's say you have a "users" collection in your MongoDB database, and each document in that collection represents a user with properties like name, email, and age. You can use Mongoose to create a "User" model, define the user's schema, and use that model to create new users, fetch them from the database, update them and delete them. Instead of using MongoDB commands to work with the data, you can use the methods provided by the model, which are more straightforward and intuitive.

It's simpler to think about it as an ORM (Object-Relational Mapper), But instead of SQL databases and tables, it uses MongoDB collections and documents.