Microsoft Defender Application Guard for Office is a new security feature designed to load untrusted Office documents, e.g. an Excel spreadsheet downloaded from the Internet, in an isolated environment to keep the underlying system and its data protected against potential attacks.
The security feature is based on Microsoft Defender Application Guard, which is designed to load untrusted sites in an isolated container using automated and standalone modes….
https://www.ghacks.net/2020/09/15/microsoft-defender-application-guard-for-office-explained/
