(1) Webserver serves pages for viewing in web browser, 
application server provides exposes businness logic for 
client applications through various protocols 

(2) Webserver exclusively handles http requests.application 
server serves bussiness logic to application programs 
through any number of protocols. 

(3) Webserver delegation model is fairly simple,when the 
request comes into the webserver,it simply passes the 
request to the program best able to handle it(Server side 
program). It may not support transactions and database 
connection pooling. 

(4) Application server is more capable of dynamic behaviour 
than webserver. We can also configure application server to 
work as a webserver.Simply applic! ation server is a 
superset of webserver.

web application:
-In this we don't have much control over the application.
-Application is loaded on the server whose location is may 
or may not be known and no exe is installed in client 
machine.You have to test different browsers.
-Web applications are supposed tobe test on different 
browser and OS platforms.
-web application is mainly tested for browser 
compatability,OS compatability,error handling,static 
pages,backend testing and load testing

client-server application:
-in this we have to test different components
-Application is loaded on server while the application exe 
on every client server.
-we have to test broadly categories like GUI testing on 
both sodes,functionality,load,client-server 
interaction,back end
-this environment is mainly used on intranet network.
-we are aware of no of clients and servers and their 
location in the test scinario.