NodeJS runs on a single thread which handle the requests. NodeJS handles thousands of concurrent connections with minimal overhead on a single process.
In traditional web development, for each coming request a new process spawns to handle the request. Node makes heavy use of callbacks. eg. a function to call the web service may start the calling the service api and return the controll to the environment immediately so it handle the next instruction. When web service call finished it call the callback function. So there is no blocking or wait. This was it hadles high number of requests without waiting.
NodeJS library are asynchronous, non-blocking. It means it will never wait for returning data. It handle the next task and when previous tasks done it call the callback function and execute it.
Our NodeJs development services includes above features and creating the Application which run on browser.