JavaScript
JavaScript, often abbreviated JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS.
Over 97% of websites use JavaScript on the client side for web page behavior, often incorporating third-party libraries.
HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser.
It can be assisted by technologies such as Cascading Style Sheets and scripting languages such as JavaScript.
CSS/CSS3
Cascading Style Sheets is a style sheet language used for describing the presentation of a document written in a markup language such as HTML.
CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.