Difference between AEM publish and preview servers | Adobe AEM

AEM as a Cloud Service come with an add on preview server feature to preview and experience the content as end-user. 

1. The preview server is not accessible for public users, this is stricted with the allowed IP list in AEM Cloud Manager. Hence, only those users can access whose IPs are allowed.
2. Publish content to preview server, we have to go to manage publication > then select the destination as preview

References:

• AEM aa CS preview server fundamentals | previewing content
• Access preview service