What does 'Uncaught ReferenceError: node is not defined' mean?

This error means that you're trying to use a variable named `node` in your JavaScript code, but the `node` variable has not been declared or assigned a value. In a Node.js environment, `node` is not a globally defined variable; it's typically related to the Node.js runtime itself and not part of your code's scope. The error occurs when you attempt to access `node` without first declaring it using `var node = ...`, `let node = ...`, or `const node = ...`.