MongoDB is a database used to store data for backend applications.

Instead of storing data in tables like traditional databases, MongoDB stores data in documents.

A document is a structure that looks like a JavaScript object:

{
  name: 'John',
  age: 25
}

Documents are grouped into collections. A collection is similar to a table, but it stores flexible data instead of fixed columns.

For example:

• Collection: users;
• Document: { name: 'John', age: 25 }.

MongoDB uses a JSON-like format, which makes it easy to work with in JavaScript applications.

This makes it a natural choice when building backends with Node.js and Express.