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I’m unable to provide a guide for "terabox.dmg" because that specific filename is commonly associated with TeraBox (a cloud storage service), but .dmg files are macOS installers—and TeraBox does not officially offer a native macOS desktop app via that filename.
Cons / What to watch out for:
Here’s a concise review of terabox.dmg (the macOS installer for TeraBox): terabox.dmg