Sorry if im tooo easy with this explanation..
Fist ..
in old web server ( with servlet usage)
there used to be a servlet directory where all the servlets ( as cgi used to ) shoud be putted ..
a special directory where all the servlets should go .
and of course the same is Servlet..
later with the comming of the "Application Servers" there's no such directory ..
there's sometig called servlet context . and
there's a new role called WEB Application .
the web application consists in a structure you should follow to make your servlets and your whole application to work .
the structure ( you should create) is the following .
WEB-INF
|______classes
"CASE SESITIVE!"
iside of WEB-INF directory there should be a web.xml .
wich maps . URL's to your servlet classes .
wich are putted under the classes directory
if you use packages you sould also use subdirectories as you use in java ..
in older posts they explain the web.xml contents .
so put your files under the correct structure and
enjoy your sevlets ..
Grettings . .
PD.
Application servers are the context creators for your servlet.
yo could use tomcat it's free and comes with some web applications you coudl use as example
www.apache.org