That's a "download manager". When you run it, it will fetch the larger installer(s) to your Documents\MAGIX Downloads\Installationsmanager\ folder.

More info here, along with some direct links to the big installers if you need them: https://www.vegascreativesoftware.info/us/forum/faq-where-can-i-download-vegas-pro-and-other-vegas-software--104782/