In this article, we will see the difference and similarities between PowerApps Portals and Power Pages.
PowerApps Portals
PowerApps Portals are an extension of PowerApps that enables both citizen developers and professional developers to build external facing-websites that allow users their organizations to sign in with a wide variety of identities, create and view data in Microsoft Dataverse, or even browse content anonymously.

Power Pages
Microsoft Power Pages is a secure, enterprise-grade, low-code software as a service (SaaS) platform for creating, hosting, and administering modern external-facing business websites. Whether you’re a low-code maker or a professional developer, Power Pages enables you to rapidly design, configure, and publish websites that seamlessly work across web browsers and devices.

PowerApps portals and Power Pages


References:
The above information taken from the below blog.
https://techcommunity.microsoft.com/t5/educator-developer-blog/differences-between-powerapps-portals-and-power-pages/ba-p/3571229
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