What is the asterisk for in signal and slot connections?

In Python Qt, I'm connecting a QListWidget signal to a slot, like this:

QtCore.QObject.connect(self.myList, QtCore.SIGNAL("itemClicked(QListWidgetItem *)"), self.ListEventHandler)

My question is: what does the trailing asterisk in QListWidgetItem * do?

Solution

A couple of bullet points to explain (I'll try to avoid C++ syntax):

PyQt is a Python wrapper around Qt, which is written in C++.
Qt provides introspection for classes inheriting from QObject, frequently using strings to identify things. Python has native introspection, but C++ does not.
The syntax that you used is called "Old-Style Signals and Slots", which uses the C++ function signatures.
C++ has more types of variables than Python. In C++, a variable can be a value, reference, or pointer. Pointers have an asterisk after their type name.
QtCore.SIGNAL("itemClicked(QListWidgetItem *)") refers to a Qt signal called itemClicked that has a parameter that is a pointer to a QListWidgetItem, not the item itself.

In C++, this looks like:

 void itemClicked(QListWidgetItem *item);

Going back to strings for introspection, to identify a signal or slot, you drop the void, the ;, and the variable name (item), leaving:

 itemClicked(QListWidgetItem *)

Wrap the above in QtCore.SIGNAL() and a pair of quotes and you have:

QtCore.SIGNAL("itemClicked(QListWidgetItem *)")

What is a pointer?
There are a number of SO questions about this. Here is one with a number of analogies in the answers to simplify things for you.

If this is old-style syntax, what's new style?
Thanks to Frodon for bringing this up. PyQt has a more "pythonic" method of connecting signals to slots, in the format:

object.signalName.connect(otherObject.slotName)

In this case:

self.myList.itemClicked.connect(self.ListEventHandler)