if i set priority 0 then what happen in testng code example

Example: how to set priority in testng

If we do not prioritize the test methods, then the test methods are selected 
alphabetically and executed. If we want the test methods to be executed 
in the sequence we want, then we need to provide the priority along with 
the @Test annotation.

@Test(priority=2)  
public void test1()  
{  
System.out.println("Test1");
}