How Queue Sorting Method Work In Pseudo Code

This was shown in class the other day and I'm still not sure of how exactly it works, even after looking at it through a debugger.

public void sort(){
for (int i = 0; i < size; i++) {
Node temp1 = head;
Node temp2 = head;
Node temp3 = head;
while(temp2.next!=null){
temp3 = temp2.next;

[Code]...

Again, I didn't write this code I'm just trying to understand it. Why specifically do three different temp values need to be used instead of just one like in most sorts?

It is part of a larger program that can be found below.

import java.util.Random;
public class MyQueue implements IntegerQueue{
class Node{
Node next;
Integer data;
Node(Integer data){
this.data = data;

[Code]....