Nothing changes. What’s the fun in that? The greatness of PostCSS is found in PostCSS plugins.
PostCSS plugins read and modify the AST before it’s turned back into a stylesheet. There are plugins to automatically add [vendor prefixes] to properties and selectors, or interpret Sass-like [variables], [mixins], and [loops], or down-mix [future] and [experimental] features to CSS. PostCSS plugins can even generate entirely new documents based on the CSS, like [styleguides].
Writing a PostCSS plugin is remarkably simple, thanks to its solid API. Still, one of the first challenges aspiring plugin authors face is importing other files. In other words, replacing links in a stylesheet with the contents of those links. This is where something like `@import