Web development can be broken down into Front-end coding versus Back-end coding. Front-end code works in a web browser, whereas the back-end code works on a web server. The front-end of websites involve coding HTML, CSS, and JavaScript that control the look and feel of a website. The back-end of a website involves coding languages such as PHP, MySQL, Ruby on Rails, Node.js, etc. to create application-like functionality that typically interacts with a database.
To create web pages and emails we use HTML code (Hypertext Markup Language). HTML tags mark up (label) content to indicate headings, paragraphs, lists, links, images, and more.
CSS (Cascading Style Sheets) code is used to style the contents of a webpage (or email), based on the HTML markup. CSS controls the appearance of everything, from fonts and color to building responsive page layouts that look good across screen sizes (mobile, tablet, and desktop).
JavaScript code is used to add interactivity, animation, and more to the front-end of websites (what you see in a browser). Create slideshows, image galleries, validate forms, and much more. JavaScript can also be used on the back-end of websites to execute code on a web server. jQuery is the most popular JavaScript library, and it makes it easier to target elements, handle events, and more.