jquery-ui-tab: Why $('a', ui.panel).click(function() does not affect any links outside the tab?

jquery-ui-tab: Why $('a', ui.panel).click(function() does not affect any links outside the tab?


I'm reading the documentation in jquery ui tabs, it said:
"Hijax" links after tab content has been loaded:
$('#example').tabs({
load: function(event, ui) {
$('a', ui.panel).click(function() {
$(ui.panel).load(this.href);
return false;
});
}
});
Why "$('a', ui.panel)" is correct? My understanding is that after the
tag is loaded, the selector will select all 'a' AND the ui.panel
element to override the click event. Isn't ',' is "Matches the
combined results of all the specified selectors."? I tried "$
(ui.panel, 'a')" and it does not work anymore.
I know the demo code is correct but I just can't understand why.
Thanks.