In jQuery, event namespaces are related to a particular feature of the bind() and unbind() methods. These methods accept a period-separated list of event namespaces attached to the main event name. Without namespaces, you're forced to remove a given event handler in this way:
$(element).unbind('click', handler);
Instead, you can use event namespaces as follows:
$(element).bind('click.myEvent', handler);
$(element).unbind('click.myEvent');
Using namespaces, you're not forced to refer directly the handler passed to these methods, but only its namespace. You can remove multiple handlers with namespace as once:
$(element).unbind('click.myEvent.anotherEvent');
The syntax used here is much similar to the syntax used for CSS classes. You can even remove a namespace handler without specifying the type of event you're using:
$(element).unbind('.myEvent');
In this case, the handler is removed regardless of the event type.