Well that depends.<BR>Are you talking webservers and app servers in general or specific to MS products.<BR>First the Definitions(kinda):<BR>App servers are servers that host a portion of an application that comes in 2 parts (client/server).<BR>Web servers are servers that server web pages(.htm/.html,.asp,.aspx...). The difference is that the application hosted by the app server has nothing to do with web. These are actual Win32 apps or their *n*x couterparts.<BR><BR>If you're talking specifically MS then the difference is not that big. Application Server is actuall a product name for a program that is designed to help web farms. It allows you to replica/duplicate IIS metabases and web content across WLBS and other types of clusters. This is a very awesome product that is replacing CRS (Content Replication Server).<BR><BR>Since you're on this forum I guess you mean the second.