Kumar,
Servlet alias means you are calling a servlet with another name of your choice at the URL.
It is always good idea to keep the servlets inside packages and deploy. Assuming you have a LoginServlet kept like this.
com.company.dept.project.LoginServlet.
It need not have this much depth level. What I use is one level depth like MISApp.LoginServlet.
So when we make a request from a url we write like this.
Instead of calling the Servlet with its package name like above everytime, we may choose to have a simple name like this
This means we made an alias for MISApp.LoginServlet as just 'LoginServlet'. For this we have to edit web.xml file and add entries for LoginServlet as Bill stated above. If the servlet container supports Servlet 2.2 API web.xml is the place to write all aliases for servlets.

regds
maha anna
[This message has been edited by maha anna (edited December 09, 2000).]