any one tell the answer

Method signature means method name and parameter list and also 
order of the parameter these three define's the mathod
signature

method signature means:-
1. Name of method.
2. Type of arguments.
3. Number of arguments.
4. Order of arguments.

method signature means defind the method in diff signature 
diff no arguments
diff datatype if arguments
diff sequence of arguments
for example

public class PolyOverload1 
{
   public int iEmpNo;
   protected double dbSalary;
   private boolean boolPermanent;
   String strEmpName;

   public PolyOverload1()
   {
      System.out.println("PolyOverload constructor");
      iEmpNo = 1001;
      strEmpName = "Base Employee";
      dbSalary = 20000.500;
   }

   public void getEmpDetails()
   {
      // to print the employee details
      System.out.println("Emp no : " + iEmpNo);
      System.out.println("Emp name : " + strEmpName);
   }

   //no of arguments difference
   public void getEmpDetails(int eno)
   {
      //to print the employee details
      System.out.println("Emp no [getEmpDetails(int eno)]
 : " + eno);
      System.out.println("Emp name [getEmpDetails(int 
eno)] : " + strEmpName);
   }

   //different type of data type 
   //note : return type can be different for overloading
   public int getEmpDetails(String ename)
   {
      // to print the employee details
      System.out.println("Emp no [getEmpDetails(String 
ename)] : " + iEmpNo);
      System.out.println("Emp name [getEmpDetails(String 
ename)] : " + ename);
      return iEmpNo;
   }

   //no of arguments difference
   public void getEmpDetails(int eno, String ename)
   {
      // to print the employee details
      System.out.println("Emp no [getEmpDetails(int eno, 
String ename)] : " + eno);
      System.out.println("Emp name [getEmpDetails(int eno, 
String ename)] : " + ename);
   }

   //different seguence type of data type
   public void getEmpDetails(String ename, int eno)
   {
      // to print the employee details
      System.out.println("Emp no [getEmpDetails(String 
ename, String eno)] : " + eno);
      System.out.println("Emp name [getEmpDetails(String 
ename, String eno)] : " + ename);
   }

   public static void main (String arg[])
   {
      //Object creation 
      PolyOverload1 polyObj = new PolyOverload1();
      //static binding or early binding...during compile 
time JVM will find that the method's reference to call
      polyObj.getEmpDetails();
      polyObj.getEmpDetails(1002);
      polyObj.getEmpDetails("Test Employee1");
      polyObj.getEmpDetails(1003, "Test Employee2");
      polyObj.getEmpDetails("Test Employee3", 1004);
   }
}

It consists of method name and type of the parameters

void sum(int a,int b){}

sum(int,int) is the method signature

In a class we cannot have two methods with the same method 
signature