Definition:

CSS, which stands for Cascading Style Sheets, is a style sheet language used for describing the look and formatting of a document written in HTML or XML. CSS defines how elements on a web page should be displayed, including their layout, colors, fonts, and other visual properties.

The primary purpose of CSS is to separate the structure of a document from its presentation. By using CSS, web developers can control the appearance of multiple web pages by making changes to a single style sheet, rather than having to update the styling information for each individual page.

Here are some key aspects of CSS:

1. Selectors: Selectors are patterns that match elements on a web page. They allow you to target specific HTML elements or groups of elements to apply styles.
2. Properties: Properties are the styling attributes that you apply to the selected elements. Examples include color, font-size, margin, padding, etc.
3. Values: Values are assigned to properties and define how the styling should be applied. For example, the color property might have a value of “red” or “#00ff00” (green).
4. Box Model: The box model is a fundamental concept in CSS that describes how elements are laid out on the page. It includes properties like margin, border, padding, and content.
5. Layout: CSS is used to control the layout of a web page, including the positioning of elements, their size, and how they respond to different screen sizes.

CSS can be applied in various ways, including inline styles (directly within the HTML element), internal styles (defined in the <style> tag within the HTML document), and external styles (stored in separate CSS files and linked to the HTML document).

By combining HTML for structure and content with CSS for styling, web developers can create visually appealing and consistent websites. Additionally, CSS is often used in conjunction with JavaScript to create dynamic and interactive web pages.