Database, Collection, Document and Field

Every query you write names these four things, whether you think about them or not.

1. 01MongoDB server
2. 02Database — app
3. 03Collection — users, orders, products
4. 04Document — Rahul
5. 05Field — city, skills, isActive

use app
db.users.findOne({ name: "Rahul" })

{
  _id: ObjectId("64a1b2c3d4e5f6a7b8c90001"),
  name: "Rahul",
  age: 28,
  city: "Bangalore",
  role: "developer",
  skills: ["Node.js", "MongoDB"],
  isActive: true
}

• Database — the application-level container. One backend usually has one (maybe a second for tests). Named app here.
• Collection — a group of related documents. users, orders, products, reviews, employees, departments. Close to a table, without a fixed set of columns.
• Document — a single record. Rahul is one document in users.
• Field — a property on that document. city is a field; skills is a field whose value is an array.

In SQL: database → table → row → column. In MongoDB: database → collection → document → field. The next two lessons are about what those field values actually are (_id, dates, decimals).