Mongoose is a popular Object Data Modeling (ODM) library for MongoDB and Node.js. It helps in dealing with database-related logic in Node.js easily by providing features like schema-based data validation, pre and post hooks, middleware, and many more.

Mongoose maps objects in the Node.js application to documents in the MongoDB database. When working with Mongoose, you define a schema that is a blueprint for the format and structure of your data. Once the schema is defined, this can be used to create Model which represents the data in the database.

With Mongoose, you don’t need to write raw MongoDB queries to interact with the database. Instead, you can use Mongoose APIs to perform CRUD (Create, Read, Update, and Delete) operations.

Mongoose provides various built-in data types such as String, Number, Date, and Boolean, and you can also define your custom data types. Moreover, it supports features like nested schemas, virtual properties, unique keys, indexing, populating documents, and transactions.

Overall, Mongoose simplifies the process of writing Node.js applications that interact with MongoDB by providing a high-level API that hides away the complexity of the raw MongoDB driver.