Currently I made a simple app with react, it works perfectly and I use react-scripts. I installed React by following the Facebook github page, and it written that "When you're ready to deploy to production, running npm run build will create an optimized build of your app in the build folder. ". After I press npm run build, a folder build created, but I do not know what to do with this folder. I tried some method like, move all folders except build and npm run, but it did not work. Anyone can explain me what is this folder "build" ? Thank you