In this post I describe what Microsoft provides with PowerApps Portals (in Preview, August 2018) to enable external users (not within your company) to access your PowerApps-based business apps.
What’s PowerApps at all?
Microsoft PowerApps is basically an app toolbox which you can use to quickly build business apps without being a developer because you can build a business app by clicking it together. It’s part of Office 365 and allows to use what you’ve already got there (Office 365, Dynamics 365 …) or (partially) elsewhere.
What’s PowerApps Portals?
Before the introduction of PowerApps Portals all users need to be within your Office 365 tenant to access your PowerApps-based business apps. PowerApps Portal is a game changer it let’s external users access your business apps via WWW on a public accessible website. You can also control access to the portal, e.g. anonymously, LinkedIn, Microsoft ID, Azure AD account, SAML2, OpenId Connect or else.

Conclusion, opinion and summary
PowerApps Portals is very handy for you if you need to build a business app which is not only accessible for your employees or users which are member of your Office 365 tenant. To enable a wider accessibility to PowerApps can enable more interaction with external users to your company.