When animating any object or element on a page, we can simply slide it up or down or move it from one place to another on the page. These are perfectly valid effects, but they lack the realism you might get when opening a drawer, for example.
Animations don't always move at a constant speed; instead, we might get a little bounce back if we were bouncing a ball or a slow down when opening a chest of drawers. To achieve this effect, we need to use easing functions, which control the rate of change. There are plenty of examples available on the Internet—a great place to start is http://www.easings.net—or perhaps we can watch the effects on sites such as http://matthewlein.com/ceaser/. Over the next few pages, we're going to explore these in more detail and look at tips and tricks that we can use to push our animation skills to a new level.