whenever u r going to run any servlet first u should place that class file in WEB-INF\classes folder irrespective of server this is the common tree in every server. We will register the servlet class name in web.xml file, there servlet container searched for realted class file in classes folder and their respective package folder like this container knows the servlet class file.
you might get better responses if you use a form of English that people can actually understand. Punctuation, proper spelling (you are instead of "u r", as soon as I see things like that I stop reading and many with me), proper placement of questions (this is definitely NOT a JSP question), etc. etc. all help too.
As to your question, it's defined in the web application configuration contained in the relevant web.xml file.
For the true and correct details of the servlet API - why not read the servlet API? From this Sun web site you can download the authentic material. Bill (I agree with Jeroen - you are not being charged by the character here - why not write complete sentences? Think of it as practice for your next job application.)