VOCABULARY, It matters -> Dynamics 365 Sales, Dynamics 365 Service, Dynamics 365 Marketing these are all Power Apps.
One of the huge transitions for the Dynamics 365 CRM world is a shift in vocabulary and terminology and aligning what the experienced resources know (Dynamics 365 CRM or Dynamics 365 CE) with all the new buzz and development options.
One way to think of this shift is that all of the modules in Microsoft Dynamics 365 Customer Engagement are "potentially" their own Power App. So it is true you can combine sales, service, marketing, talent, etc. into one app, but basically the thinking trend is that each module is a Power App.
The other way that I have found that people quickly grasp the concept is to mention MOBILE and get them in a mobile mindset. I can then say, you can create any number of mobile apps to access your Dynamics 365 Customer Engagement data. Each mobile app is a PowerApp.
And as such the Power Platform offers the potential for hundreds of Power Apps, as well as other complimentary technologies such as Power BI, Power Automate and Power Virtual.