What is SharePoint Web Front End server (WFE)
The Web Front End (WFE) server is a server that handles web page requests from users. Thus, each time the user opens a SharePoint page in a browser, it is processed by the WFE server. SharePoint farm may have several such servers. In this case, Network Load Balancer is distributing requests between them. It is the way to scale SharePoint.
Org Chart for SharePoint on-premises is licensed per Web Front End server. You may need to calculate the number of the WFE servers on your farm to purchase the correct number of licenses.
Note
It may occur that the Load Balancer distributes the user requests only among some of WFE servers. In this case, you will need licenses not for all of them but only for the part that actually handles the requests.
SharePoint 2013
In this version of SharePoint, the WFE server usually has the “Microsoft SharePoint Foundation Web Application” service started. You can check it in SharePoint Central Administration: Central Administration > System Settings > Manage services on server. On the “Services on server” page, select a server and check if the service is started. If it is, most likely, the selected server is acting as a WFE server.
Thus, you can switch between your servers and find all WFE ones.
SharePoint 2016/2019/SE
In this version of SharePoint, you can find the roles of servers in the “Farm information”: Central Administration > System Settings > Manage servers in this farm. The WFE servers will have a “Front-end” role:
