It is a single-threaded asynchronous concurrent loop. A single thread can do one thing at a time. In the event loop, multiple requests can get queued at the same time and that makes it concurrent. Loop doesn’t wait for everything from one request for complete but callback comes without blocking anything.
It is a semi-finite type loop where if the queue is empty, the loop will automatically exit. Node.js uses libuv in the operating systems for callbacks for incoming connections.
To speak about web monetization is to speak about web advertising and user data. When accessing free content you are handing your personal data or getting bombarded with ads. Most likely both.