There are occasions when you have already selected elements and need to add more items to it. Imagine you have selected different items and have jQuery selection object. For example:
var elms = $('#elem, .items');
Now, you need to add more new items (DOM nodes) to your section. Let’s say you want to add .otherItems to your elms selection. You could achieve it by using one of these methods:
elms.add('.otherItems');
$('.otherItems').add(elms); // The same as above
The post title for the second method would be “How to add jQuery object/selection to the existing selection”. Anyway, it’s just wording :)