jQuery makes it fairly easy to animate DOM elements. Animating a single-step animation on one or more elements is simple with the call of the
animate method. Multi-step animations can be more complex because animations are run asynchronously, meaning that they will start running when called but the script will continue onto the next step before the animation is done. For these, jQuery has the ability to queue steps. jQuery automatically queues multiple steps on a single object and dequeues as each completes, so you don’t have to worry about managing things and setting up callbacks. But for more complex animations where multiple elements are animated at different times or other functionality must be performed after an animation step, there is no automatic queuing.
A common practice for simple queuing is to use the “complete” parameter of the animate method or of other similar asynchronous methods that is a callback to be run when the animation is finished. This works nicely when there are a few steps. It becomes more unwieldy though the more steps you add. That is where
queue comes in, allowing for adding of as many steps as you want without having to nest in callback after callback.