Until now, we've been dealing entirely with methods that are called on a jQuery object. For example:
Most jQuery methods are called on jQuery objects as shown above; these methods are said to be part of the $.fn namespace, or the "jQuery prototype", and are best thought of as jQuery object methods.
However, there are several methods that do not act on a selection; these methods are said to be part of the jQuery namespace, and are best thought of as core jQuery methods.
This distinction can be incredibly confusing to new jQuery users. Here's what you need to remember:
There are a few cases where object methods and core methods have the same names, such as $.each and $.fn.each. In these cases, be extremely careful when reading the documentation that you are exploring the correct method.
A common practice is to use $(selector) to obtain collections, and jQuery (rather than $) to invoke the core methods.