The jQuery function is a factory for creating a jQuery object that represents one or more DOM nodes.
jQuery objects have methods to manipulate these nodes.
These methods (sometimes called commands), are chainable as each method also returns a jQuery object.
Access to and manipulation of multiple DOM nodes in jQuery typically begins with calling the $ function with a CSS selector string.
This returns a jQuery object referencing all the matching elements in the HTML page.
$("div.test"), for example, returns a jQuery object with all the div elements that have the class test.
This node set can be manipulated by calling methods on the returned jQuery object.