Summary  
This chapter introduces Cascading Style Sheets (CSS) as a language for separating content structure from visual presentation by using selectors and declaration blocks to define properties like colors, spacing, and fonts.  

General domain of usage  
Web development

HTML defines the structure and content of a web page.
 CSS defines how that content is presented.

While HTML organizes elements such as headings, paragraphs, and images, **CSS controls** their **appearance**, including colors, spacing, fonts, alignment, and layout.

Together, HTML and CSS form the foundation of modern web development.

CSS stands for Cascading Style Sheets.
It is a stylesheet language used to describe how HTML elements should be displayed in a browser.

Definition

With CSS, you can:
- Change text and background colors;
- Adjust spacing between elements;
- Control fonts and typography;
- Create layouts;
- Add visual effects.

CSS does not change the structure of a document.
 It controls how that structure looks.

## Basic CSS Syntax
A CSS rule consists of a selector and a declaration block.<br>
Example:
```css
p {
  color: purple;
  background-color: green;
}
```
Explanation:
- `p` is the selector. It targets all `<p>` elements;
- `color: purple;` sets the text color;
- `background-color: green;` sets the background color.

Each declaration follows this format: `property: value;`

You will explore selectors, properties, and values in detail in upcoming chapters.

Master the essentials of CSS, the styling language that transforms the look and feel of web pages. Explore core concepts such as text styles, colors, spacing, the box model, Flexbox, and decorative effects. Build the skills to create visually engaging and well-structured web pages.

Understand how CSS connects to HTML and how styles are applied through selectors. Apply colors, text styling, and hover effects to control visual presentation.

Improve typography using line height, spacing, font properties, and custom fonts. Control font families, weight, style, and size for better readability.

Control layout structure using margin, padding, borders, and width properties. Understand box sizing behavior and element display types such as block, inline, and inline-block.

Control horizontal and vertical layouts using Flexbox properties. Adjust direction, alignment, and spacing to structure UI components.

Enhance layouts using background colors, images, pseudo-elements, and shadows. Style visual components for depth and contrast.

What CSS Is and Why It Matters

What Is CSS?

Basic CSS Syntax