# What is CSS and How Does It Work?
# What is CSS and How Does It Work?
*13 Oct 2019 22:12 (Updated for 2026 Modern Design Standards)*
![CSS Development Concept](https://iformatlogic.com/storage/cms/posts/featured/1571033526_1.jpg align="center")
**CSS** stands for **"Cascading Style Sheets."** While HTML is used to build the structure of a website, CSS specifies the design. Page layouts, colors, and fonts are all determined by CSS.
Think of it this way: **HTML is the foundation and framing of a house, while CSS is the paint, the window styles, and the landscaping.**
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## ⚙️ How Does CSS Work?
CSS brings style to your website by interacting with HTML elements. To change the look of an element, you use a "rule set" consisting of a **selector** and a **declaration**.
### The Anatomy of a CSS Rule:
If you have a paragraph in HTML: `
This is my paragraph!
`
To make it blue and bold, your CSS would look like this: `p { color: blue; font-weight: bold; }`
* **Selector:** The `p` tells the browser which HTML element to style.
* **Declaration:** Everything inside the curly brackets `{ ... }`.
* **Properties & Values:** `color` is the property, and `blue` is the value.
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## 🛠️ Three Ways to Implement CSS
There are three main methods for adding CSS to your HTML pages. Choosing the right one depends on the scale of your project.
### 1\. External Style Sheets (The Most Efficient)
External sheets are saved as `.css` files. They allow you to change the look of an entire website by editing just one file. You link it in your HTML `` like this: ``
### 2\. Internal Style Sheets
These are written directly into the `` of a specific HTML page using `