How to ensure that a server act as a web server and not as application server?

I have 3 servers that have SharePoint 2013 installed, how should I know if the servers I named as WFESERVER can really act as web server. There is a question in this group also and someone answered that if a server has a service of Microsoft SharePoint Foundation Web Application then it can act as web server, but in my case, my APPSERVER has this service also. Kindly enlighten me on this. Do I just need to stop the service Microsoft SharePoint Foundation Web Application in my APPSERVER so that the WFESERVER servers will act only as web servers?