Can someone Help me to understand how popper.js imported the library in rollup.config.js and how it include in the compiled file? does popper.js is part of the bootstrap compilation?

Then this code is declaring popper.js to “popper” as global variable?

const globals = { jquery: 'jQuery',
'popper.js': 'Popper' } Is that how it’s been imported?

Please enlighten my knowledge.
Thank you.