What is the difference between transpiling syntax and polyfilling APIs — how do Babel, core-js, and browserslist work together, and what does differential serving change?

Imagine you're building with LEGOs, but your friend has an older set. Transpiling is like rewriting your instructions in their language, while polyfilling is like giving them the special bricks they're missing. Babel, core-js, and browserslist work together to make sure your code runs on everyone's LEGO set, no matter how old.