The .dmg file is the for Apple Remote Desktop. Historically, Apple distributed ARD as a downloadable DMG from its website (for licensed users). Today, the main purchase/delivery method is the Mac App Store → installs directly without a visible DMG.
Best for easy, secure access across Mac, Windows, and mobile devices. apple remote desktop dmg
Unlike the Admin tool, client capabilities are built into macOS. You do not need a DMG for clients. To enable remote management on client Macs: secure access across Mac