- ObjectID (12 bytes HEX string) = Date (4 bytes, a timestamp value representing number of seconds since the Unix epoch) + MAC address (3 bytes) + PID (2 bytes) + Counter (3 bytes)
- A Schema is an object that defines the structure of any documents that will be stored in your MongoDB collection; it enables you to define types and validators for all of your data items.
- A Connection is a fairly standard wrapper around a database connection.
- A Model is an object that gives you easy access to a named collection, allowing you to query the collection and use the Schema to validate any documents you save to that collection. It is created by combining a Schema, a Connection, and a collection name.
- Finally, a Document is an instantiation of a Model that is tied to a specific document in your collection.
- Mongoose can’t handle multi-level population yet, and populated fields are not Documents.