High-Level
JavaScript adds interactivity to web pages and online applications. The DOM is an object representation of every element on a website. Together, they transform static web pages built with HTML and CSS into vibrant, dynamic web pages and applications. User events, interaction with other websites, transaction with applications - all of this and more is possible with these combined technologies.
Key Technologies
JavaScript
powers the internet - it is the most widely-used web programming language in the world and adds interactivity and functionality to websites
React
(or ReactJS) is a front-end library developed by Facebook. It handles the view layer for web and mobile apps through reusable UI components.
DOM
(The Document Object Model) is a language-agnostic programming interface that features an object-oriented representation of a web page which can be modified by scripting languages
axios
(yes, its all lowercase) is a lightweight, promise-based HTTP client designed to take advantage of async and provide more readable asynchronous code. It gets data from online servers.