text: A Servlet is a class, which implements the
  javax.servlet.Servlet interface. However instead of directly implementing the
  javax.servlet.Servlet interface we extend a class that has implemented the interface like
  javax.servlet.GenericServlet or
  javax.servlet.http.HttpServlet.
  Servlet Exceution
  This is how a servlet execution takes place when client (browser) makes a request to the webserver.
  Servlet architecture includes:
  a) Servlet Interface
  To write a servlet we need to implement Servlet interface. Servlet interface can be implemented directly or indirectly by extending GenericServlet or HttpServlet class.
  b) Request handling methods
  There are 3 methods defined in Servlet interface: init(), service() and destroy().
  The first time a servlet is invoked, the init method is called. It is called only once during the lifetime of a servlet. So, we can put all your initialization code here.
  The Service method is used for handling the client request. As the client request reaches to the container it creates a thread of the servlet object, and request and response object are also created. These request and response object are then passed as parameter to the service method, which then process the client request. The service method in turn calls the doGet or doPost methods (if the user has extended the class from HttpServlet ).
  c) Number of instances
  Basic Structure of a Servlet
  public class firstServlet extends HttpServlet { public void init() { /* Put your initialization code in this method, * as this method is called only once */ } public void service() { // Service request for Servlet } public void destroy() { // For taking the servlet out of service, this method is called only once } }
  This is only one site and knowledge area where i got every solution with high commands thanking you and have a great wishes to your site.. ☺️☺️
  what is the difference between servlets and webservices
  1. Servlets provide webservices.
  2. webservices in the sense services provided by the server containing servlet container and in that servlet container we have webapplications. And webapplications may contain different servlets in order to retrive dynamic data and also process the data provided by the user.
  Thank You so much for the answer . This is the best answer i got, because it explained along with diagram and besides that the english is simple, very easy to understand ,,, It helps me alot !