How TF Does XSS Work?

tiff - Nov 12 '18 - - Dev Community

I tweeted this just 5 minutes ago:

My aim here is to fix a vulnerability of a core React component for an app I’m building I’d like to be the app to showcase on my portfolio and resume. I just don’t understand how XSS works.

Any help?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .