HTML (HyperText Markup Language) is the standard language used to create and structure content on the World Wide Web.
CSS (Cascading Style Sheets) is a stylesheet language used to control the look and layout of web pages.
Bootstrap is a free, open-source front-end framework developed by Twitter in 2011 (originally by Mark Otto and Jacob Thornton).
JavaScript (JS) is a lightweight, high-level, interpreted programming language primarily used to make web pages interactive and dynamic.