Middleware is a function that runs between receiving a request and sending a response.

It has access to the request, the response, and a special function called next.

app.use((req, res, next) => {
  console.log('Request received');
  next();
});

When a request comes in, middleware runs first. After it finishes, it calls next() to pass control to the next step.

The flow looks like this:

Request → Middleware → Route → Response

Middleware is used to process requests before they reach your route logic.

Common use cases include:

• Logging Requests;
• Parsing Data;
• Checking Authentication.