$ = just happens to be a valid identifier. Often used to refer to the jquery global object
jQuery = A really popular framework. More on the basics http://learn.jquery.com/about-jquery/how-jquery-works/
# and . = a jquery shortcut on css selectors. # selects HTML elements by ID, while . selects by name. So “#row” selects all elements with ID row, while “.row” selects all elements. More on their CSS selectors http://api.jquery.com/category/selectors/basic-css-selectors/
function() = just happens to be a default function name used in jQuery.
btw, single quotes or double ‘ vs ” are both valid. Use whichever suits your style. But be consistent. I use single quotes as it implies a program character, as opposed to content character.
jsfiddle is absolutely amazing. http://doc.jsfiddle.net/tutorial.html