Autoprefixer
ELI5 — The Vibe Check
Autoprefixer is the robot that adds -webkit-, -moz-, and all those annoying vendor prefixes to your CSS so you don't have to. Write normal CSS, and Autoprefixer checks Can I Use data to add exactly the prefixes needed. It's the intern that does the boring work perfectly.
Real Talk
Autoprefixer is a PostCSS plugin that automatically adds vendor prefixes to CSS rules based on Can I Use data and your target browser configuration. It processes standard CSS and adds only the necessary prefixes for your supported browsers, removing outdated ones.
When You'll Hear This
"Just write standard CSS and let Autoprefixer handle the prefixes" / "Autoprefixer removed our old -webkit- prefixes that aren't needed anymore"
Related Terms
Babel
Babel is the universal translator for JavaScript.
Polyfill
A polyfill is a piece of code that teaches old browsers new tricks. Browser doesn't support Promise? Here's a polyfill that fakes it.
PostCSS
PostCSS is a CSS processor that does... whatever its plugins tell it to do. It's like an empty pipeline where you plug in transformations. Autoprefixer?