Microsoft introduced Single Part App Pages to host SharePoint Framework web parts or Teams applications in SharePoint Online with locked layout. 

Applicable For

• Modern Communication Site
• Modern Pages

Limitations of Single Part App Pages

1. It cannot be edited by end users using browser
2. It currently supports hosting only single web part or Microsoft Teams application (This becomes an advantage for ShortPoint webpart because you can use our Section and Rows layout to have multiple elements in single webpart)
3. Page layout can only be changed pragmatically from normal page layout to a Single Page App Page

Advantages of Single Part App Pages

1. No action commands visible on page like New, Edit, Comment, Page Title, etc..
2. Since the layout is locked, you can have better governance 

How to Configure Single Part App Pages

1. Using JavaScript
2. Using PowerShell
3. Using Office 365 CLI