HTML and CSS are the basic building block of web development hence it is the most important skill you must have.
JavaScript helps you to build dynamic, responsive, fully-functional, and feature-rich web applications.
Front-end development involves various skills such as the programming language, frameworks (React, Angular, etc. ), tools, libraries, VCS, and IDEs.
The backend handles the data which plays an important role in web applications. It is the back end that integrates the front end with the data.
NPM is a library for JavaScript software packages. NPM plays a critical role while web development as it helps you to install the necessary libraries or files and manage the dependencies required while building the application.
The database management system is indeed an important skill developers must have. You need to handle large amounts of data while running an application, thus to maintain it, you need a DBMS.