Thanks for answering so quickly!
OK, now I see how it works. I’m building a site which starts in Spanish which will later be translated into English.
So I need to start the project with the core site: “mysite.com/es/” for SEO purposes.
If I started it with just “mysite.com” and then later changed it to: “mysite.com/es”, this would mean setting up a redirect for Spanish users. Or, when the English version goes live or by changing the settings, get Google to reindex everything again in Spanish with the “es” directory (but that could screw-up my SEO if I have inbound links).
Anyway, I just wanted to start out by taking the initial site with the “es” for indexing purposes and later have the “en” version added. This way, everything is setup correctly right from the start.
I hope you see what I mean (!)