What do dot and hash symbols mean in JQuery?
The hash (#) specifies to select elements by their ID's
The dot (.) specifies to select elements by their classname
You can read more about the selectors here: http://api.jquery.com/category/selectors/basic-css-selectors/
$('.row') will select any element with class="row"
$('#row') will select the element with id=row
Check the jQuery page on selectors.