GridFS is a MongoDB feature that stores large binary files by breaking them into smaller chunks and saving them in two collections: `fs.files` and `fs.chunks`. The `fs.files` collection contains metadata for the document, while the `fs.chunks` collection contains the actual binary data. This allows developers to easily store and retrieve large files without having to write custom code to break them up into smaller chunks. GridFS provides a simple API for inserting, retrieving, and deleting binary documents, making it easy to build applications that require storing and serving large files. The feature is designed to be efficient and flexible, allowing developers to customize the metadata fields used in the `fs.files` collection as needed.