Sure, Node.js is a reputed runtime environment that allows a given user to run JavaScript code on the server. It is well-regarded for its massive package ecosystem and event-driven architecture.This makes it great for building efficient and scalable web applications.

Sure, this is a web application framework that is created on top of Node.js. Express.js offers a host of features such as static file serving, templating, middleware, routine, and streamlining the development processes for web applications.You can consider it as a facility for creating web apps with Node.js.

It is best to make use of Node.js if you require building real-time applications or a JavaScript runtime environment for server-side scripting.Furthermore, it is a wonderful choice if you are looking to leverage JavaScript’s familiarity throughout your back-end and front-end development.

You should make use of Express.js when you are creating a web application on Node.js. It offers a robust and structured approach with features such as middleware and routine.This will make development more organised and quicker.

Of course, you can go with Java with Spring and Python with Django for different server-side languages. With microservices architectures in Node.js, NestJS presents a host of features for modular development.

It is important to highlight that Node.js is a great foundation. Express.js can simplify web development for you. Still, properly understanding the Node.js core concepts, such as event-driven architecture, is useful prior to getting into frameworks.