Documents & BSON

What is a document?

A document is a set of key-value pairs, similar to a JSON object. Values can be strings, numbers, arrays, or even nested documents.

An example document

Notice the nested address object and the tags array — both live inside one document.

{
  name: "Ada Lovelace",
  age: 36,
  address: { city: "London", zip: "SW1A" },
  tags: ["mathematician", "writer"]
}

BSON adds more types

MongoDB stores documents as BSON (Binary JSON) — a superset of JSON with extra types like Date, ObjectId, and distinct int32/int64/double.