ActionScript 3.0 :: Error("Encountered An Error With The NumUsers Value", 99)??

I'm not sure about the purpose of the throw statement.What exactly does it do in the following example?Does it throw the error message on the screen?The manual is silent about what the throw statement does upon execution.The throw statement

Flash Player and Adobe AIR throw exceptions when they encounter errors in your application at run time.In addition,you can explicitly throw exceptions yourself using the throw statement.When explicitly throwing errors, Adobe recommends that you throw instances of the Error class or its subclasses.The following code demonstrates a throw statement that throws an instance of the Error class, MyErr,and eventually calls a function,myFunction(), to respond after the error is thrown:

var MyError:Error = new Error("Encountered an error with the numUsers value", 99);
var numUsers:uint = 0;
try { if (numUsers == 0)[code]......

Notice that the catch statements are ordered so that the most specific data types are listed first.If the catch statement for the Number data type was listed first, neither the catch statement for the uint data type nor the catch statement for the int data type would ever get executed.