Question

I remember someone telling me that the features of the Easing plugin may now be included in the jQuery core, or in jQuery UI. Is that true? Is the plugin still needed if using the current version of jQuery?

Answer 1

There are only two easing modes included in the jQuery library. From the documentation:

The only easing implementations in the jQuery library are the default,
called swing, and one that progresses at a constant pace, called
linear. More easing functions are available with the use of plug-ins, most notably
the jQuery UI suite.

Source: http://api.jquery.com/slideDown/

Here is a showcase of easing modes included in jQUery UI