Pass by value calls a function or returns a value based on the number or "value".While Pass by reference calls a function and passes a pointer to a memory location that contains the value.

Pass By Value: It refers to pass the variables or a constant that holds the primitive data type to a method.

Example:

public class PassByValue{
public static void display(int a){
a=5;
System.out.println(a);
}
public static void main(String[]args){
int i=20;
System.out.println(i);
display(i);

}
}

Pass By Reference: It refers to pass an object variable to a method.

Example:

public class PassByRefernce{
public static void display(StringBuffer sb){
sb=sb.insert(8,"to");
System.out.println(sb);
}
public static void main(String[]args){
StringBuffer sb1=new StringBuffer("Welcome RoseIndia");
System.out.println(sb1);
display(sb1);
}
}