JQuery :: How Var Selector Fits In Place Of This

I have a small function which is not entirely correct. Although it produces correct results, syntactically it's wrong. Here's the function, then I'll explain.

function displayLabelErrors(selector) {
$(selector).each(function () {
var valError = false;
$('.validation-error', this
).each(function () {
if (!$(this).attr("isvalid")) {
valError = true;
}});
$(this).toggleClass('input-error', valError);
});}

The var 'selector' is an ID and can therefore only ever be 1 object. The foreach in blue isn't required and the red 'this' (context) should be the selector. The issue I have is when I remove the loop, I'm struggling to understand how the var selector fits in the place of 'this'. I've tried a few different ways and still failing.