Web design / Website Desiging is the process of creating websites for the Internet. web design is technically a subset of the broader category of web development.
The different areas of web design include Graphic Design, User Interface Design UI, User Experience Design UX, Authoring Content / Content Writing and Search Engine Optimization / SEO.
Websites are designed using a markup language called HTML, The layout and appearance of the elements within a webpage are typically defined using CSS, Therefore, any website includes a combination of HTML and CSS code.
While HTML and CSS are used to design the look and feel of a website, images must be created separately. Therefore, Graphic Design may overlap with Web Design, since Graphic Designers often create images for use on the Web. Some graphic programs like Adobe Photoshop, Corel Draw, Illustrator etc.,.
Hypertext Markup Language (HTML) is the standard markup language for creating web pages and web applications, HTML describes the structure of a web page semantically and originally included cues for the appearance of the document.
Whereas, Cascading Style Sheet (CSS) is used to define styles for your web pages, including the design, layout and variations in display for different devices and screen sizes.
CSS is a style language that defines layout of HTML documents. For example, CSS covers fonts, colours, margins, lines, height, width, background images, advanced positions and many other things.
CSS is a style sheet language used for describing the presentation of a document written in a markup language like layout, colors, fonts,
HTML and CSS are two of the core technologies for building Web pages. HTML provides the structure of the page, CSS the (visual and aural) layout,
Some web designers prefer to hand code pages (typing HTML and CSS from scratch), while others use a "WYSIWYG" editor like Adobe Dreamweaver / other editors.
If you would like to learn about modern web design techniques, good website practices and web design standards - all in simple and understandable format, then perhaps it is best to start from here.
The most commonly used technologies to learn for one to get started as a Website Designer is to learn HTML, CSS, Photoshop, Coreldraw / Illustrator and Dreamweaver.