CSS, or Cascading Style Sheets, is a style sheet language used for describing the presentation of a document written in HTML or XML. It defines the layout, colors, fonts, spacing, and other visual aspects of a web page.

If HTML is the structure of a web page, CSS is the style that makes it look good. It controls how elements like text and images appear on the page, determining things like colors, fonts, and spacing.

Key Points:

Separation of Concerns: CSS separates the structure (HTML) and presentation (styling) of a web page. This makes it easier to manage and update the visual aspects without changing the content.

Selectors and Properties: CSS uses selectors to target HTML elements and apply styling properties to them. For example, you can use a selector to target all paragraphs and specify the font size or color.

Responsive Design: CSS is essential for creating responsive and mobile-friendly designs. Media queries within CSS enable the adaptation of styles based on the device’s characteristics, such as screen size.

Example:

/* CSS code */
body {
font-family: ‘Arial’, sans-serif;
background-color: #f2f2f2;
}

h1 {
color: #3366cc;
}

.container {
width: 80%;
margin: 0 auto;
}

In this example, CSS is used to set the font family and background color for the body, define a color for the h1 heading, and specify the width and margin for a container element.

In summary, CSS is a styling language used to control the visual presentation of web pages. It enables the separation of design and content, making it easier to create consistent and aesthetically pleasing websites.