NodeJS is a JavaScript-based backend framework for web applications that enables fast, scalable, and efficient development with high concurrency and data streams. Choosing the right database for NodeJS applications can be challenging as it depends on factors such as data type, size, complexity, performance, scalability, reliability, compatibility, interoperability, environment, and developer preference. SQL databases store data in tables with schemas and relationships, while NoSQL databases store data in various formats such as documents, key-value pairs, graphs, or columns. Realtime databases provide realtime synchronization and updates between the server and clients. Some of the best NodeJS databases include PostgreSQL, MySQL, SQLite, MongoDB, Firebase Realtime Database (RTDB), and CouchDB. These databases offer different features and capabilities that can suit various use cases and requirements for web applications.