PostCSS is an adaptable tool that processes CSS through the use of JavaScript plugins, which allows for various functionalities including linting, support for variables and mixins, transpilation of newer CSS syntax, and image inlining. Acting as a foundational framework for crafting CSS tools, it can also facilitate the development of template languages akin to Sass and LESS. At its core, PostCSS features a CSS parser that constructs an abstract syntax tree, a collection of classes that make up this tree, a CSS generator that converts the object tree into CSS lines, and a code map generator to track CSS modifications. The plugins interact with the object tree, scrutinizing and altering it prior to PostCSS producing a new CSS string that embodies these adjustments. Among its prominent plugins are Autoprefixer, which manages vendor prefixes, and Stylelint, a contemporary CSS linter that promotes uniform standards while preventing mistakes in stylesheets. Major companies like Wikipedia, Twitter, Alibaba, and JetBrains utilize PostCSS, highlighting its effectiveness and popularity in the industry. This widespread adoption underscores the tool's significance in modern web development workflows.