Easing is how the speed of the transition between CSS3 settings occurs. For example, is it linear – where the speed stays the same, or does it easeIn, where it starts slow, and progressively gets faster?
There are over 30 different ways to ease into your next transition, and http://easings.net/ has a simple way of showing you these. Just hover over an effect to see it work.
There is also a link to a jQuery plugin to show what/how to get it to work for users who are using a browser that doesn’t support CSS3 transitions yet.
Very cool indeed.
Understanding CSS3 Easings was originally found on Access 2 Learn