Frontal Servers are like web servers that handle the tracking, mirror pages, and delivery.
Tracking, Mirror pages, and images are generally hosted on Frontal Servers, so the apache access requests can be handled at the web server level and they do not increase the load on the application server.
For further details, please refer to: https://experienceleague.adobe.com/docs/campaign-classic/using/installing-campaign-classic/deploymen...