Explain what is meant by a non-relational database.

A NoSQL database is a type of database that does not use the traditional relational model with tables, rows, and columns. Instead, data is stored in other formats such as documents, key-value pairs, graphs, or columns.

Main features of NoSQL databases:

• Flexible data structure that does not require a strict schema.
• Well-suited for storing large volumes of heterogeneous data.
• High scalability and performance when working with distributed systems.

Example: MongoDB stores data in the format of JSON-like document objects, which is convenient for dynamically changing data.

Thus, NoSQL databases are used where the relational model is inconvenient or excessive, for example, for big data, caching, session storage, etc.