Easing is a fundamental concept in animation that determines how an animated property progresses over time. Instead of moving at a constant speed from start to finish, easing allows you to create more natural and visually appealing motions. The most basic type of easing is linear, where the animation progresses at a steady, unchanging rate. However, real-world movement rarely happens this way. For smoother and more realistic effects, you can use other easing types such as ease-in, ease-out, and ease-in-out.

With ease-in, the animation begins slowly and then accelerates towards the end. This mimics the way objects often start moving from a stop, gradually picking up speed. Ease-out is the opposite: the animation starts quickly and then decelerates, coming to a gentle stop. Ease-in-out combines both behaviors, starting slowly, speeding up in the middle, and then slowing down again at the end. GSAP provides a wide range of built-in eases and even lets you define custom easing curves for unique effects.

When you compare these different easing types visually, you will notice that linear movement feels mechanical and abrupt, while ease-in and ease-out create more organic transitions. Ease-in is useful for effects where an object needs to pick up speed, such as a ball dropping or a menu sliding in from the side. Ease-out works well for elements that need to settle gently, like a dialog box fading out. Ease-in-out is perfect for motions that should feel smooth and natural throughout, such as scrolling or swiping gestures. Custom eases allow you to tailor the motion curve to fit a specific brand or user experience, giving you full creative control.

Choosing the right easing function depends on the effect you want to achieve. Use linear for consistent, mechanical movement. Choose ease-in or ease-out to mimic acceleration or deceleration, and use ease-in-out for the most natural, lifelike animations. Custom eases offer endless possibilities when you want to create a unique feel for your animations.