Do my original site URLs need to be HTTPS?

Thanks for this! Sounds simple… but I’m missing a fundamental piece.

Assuming SSL is in place, do any of the native URLs for the site need to be HTTPS already? Or is the point here that all of the native URLs can be HTTP and this plugin will make everything HTTPS dynamically on the fly? I’m assuming the latter, but just making sure so I don’t blow anything up! ??