What is the difference between Office 2019 (one-time purchase) and Microsoft 365 subscription?

Office 2019 Home & Business is a one-time purchase and does not receive any feature updates after the purchase. Office 2019 includes a subset of features found in Microsoft 365, but it isn’t part of Microsoft 365. Buy Office 2019 software and you will receive quality and security patch updates as required. Microsoft 365 is the user-based cloud subscription service powered by the Microsoft cloud. It includes the most collaborative, secure, and up-to-date features.

How do I know if my PC or Mac can run Office 2019?

Office 2019 is compatible with Windows 10 or MacOS. Check the System Requirements for compatible versions of Windows and macOS, and for other feature requirements.