The Office 365 Substrate is a poorly understood part of Microsoft's Cloud Office system. The substrate is a critical part of enabling services that run across different applications like Exchange Online, SharePoint Online, Teams, and so on. Functionality like search, information protection, data governance, and eDiscovery is a lot harder when you have multiple moving parts. The substrate gives cohesion and coherence to what could otherwise be a tangled mess.
https://www.petri.com/office-365-substrate
