Microsoft Flow is an app that is part of the Office 365 suite. It is included in most Office 365 subscriptions and can be accessed by the Office 365 App Launcher. It allows you to automate business processes by building workflows based on certain triggers and actions. For example, once a new entry is added to a SharePoint list – an email can be sent asking an individual to review. Or, maybe when a document is uploaded to a document library, an email will be sent to your manager asking for an approval/feedback of the document.