Understanding the Use of @media in Style Rules

The @media rule in CSS is vital for creating responsive web designs. This rule allows developers to create specific style rules for different media types, such as screens (computer, tablet, mobile), print, and more. Full comprehension of @media is essential for any modern web developer.

Consider, @media as a conditional statement in programming. It applies specific sets of CSS properties and values only if the condition (media query) is met. For example, we might wish to change the layout of a web page when the screen's width is less than 600 pixels. It might look something like this:

@media screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}

In this example, the body's background color will change to light blue when the viewport is 600 pixels wide or less.

The importance and power of @media in web design cannot be overstated. It's a powerful tool that allows a single website to accommodate different devices and screen sizes gracefully. Without @media, developers would have to design multiple versions of a website for different devices - a time-consuming and inefficient process.

The other options "@import", "@extend", and "@debug" play different roles in CSS. The @import rule allows you to include a CSS file into another, which can be helpful for organization and code management. The @extend directive is part of SASS, a CSS precompiler, and isn't a CSS feature itself. It lets you share a set of CSS properties from one selector to another. The @debug rule is also a part of SASS, which is used to output the values of variables or expressions in your style sheets for debugging purposes.

But when it comes to defining style rules for different media types, only "@media" does the job. Understanding how and when to use it forms part of the foundation for creating effective, responsive web designs.