Unless you are installing from physical media, internet access is required to download and activate Office 2019. Is internet access required for Office 2019?.Office 365, Office 2010, Office 2013, and Office 2016 applications can open your documents without any additional action.
The Office applications available for Mac users and the specific features included may be different from those available for PC users. Office applications are tailored for each platform. See system requirements for compatible versions of Windows and macOS, and for other feature requirements. Office 2019 is compatible with Windows 10 or macOS. It includes the most collaborative, secure, and up-to-date features. Office 365 is the user-based subscription service powered by the Microsoft cloud. Office 2019 will receive quality and security patch updates as required. Office 2019 includes a subset of features found in Office 365, but it isn’t part of Office 365.
Office 2019 is a one-time purchase and does not receive feature updates after purchase.