How to determine and check if a server is a SharePoint Web front-end Server or a SharePoint Application Server?
This is not easy unless documented...
Couple of things to check to make decision..
1) from central admin > manage servers in farm...check which server is running central admin website...This is the evidence of app server.
2) check AAP settings, see which server is mentioned for your website....This is wfe.
3) ping the sharepoint Web address and see which server IP mentioned here...again this is your wfe.
Or. 4) you can check which server is running Web application services, this is required for wfe...but this one is not hard evidence because no body turn off this services for app servers.
5) for app server, this server typically run the all services applications. ..so you can check from manage services on server...which server having these...
A server is considered Web Front-end Server if its running "Microsoft SharePoint Foundation Web Application" service. The best way to check is under "Central Administration --> Services on Server" and then choose the server you are interested and check what kind of services are running on it.
There are several main criteria to consider an server a "Web Front-end Server" (WFE).
1) As others have mentioned, the "Microsoft SharePoint Foundation Web Application" must be running. However, just because this is running does not make it a WFE. Other servers in the farm, for various reasons, may also have the Microsoft SharePoint Foundation Web Application service started.
2) Condition two is that user traffic is directed to the WFEs (via DNS and/or load-balancing). That is, they are accessed by end users to get at the farm content. Typically, even if the Microsoft SharePoint Foundation Web Application service is started, if no users hit that server directly, it is probably not a WFE. An exception would be if there was a dedicated WFE for handling search crawler traffic.
3) If the Microsoft SharePoint Foundation Web Application service is not started, it is not a WFE