Here is a simple example to demonstrate the difference between the event target (where an event takes place), and the this reference (where an event handler is defined).
Consider the following hunk of HTML:
We could write an event handler like so:
Clicking on one of the list items will reveal that evtTarget references an LI element, while this references the DIV element. I like this style, but for various reasons we often wire event handlers like so:
And the script, which doesn't change a great deal:
Clicking in a list item will show us that the evtTarget is still an LI element, but this.nodeName will now show as undefined. The function List_onclick in the second example is part of the global object, which doesn't have a nodeName.