Keyframe

Set a clip's scale to 100 per cent at the start and 120 per cent two seconds later, and the editor fills in everything between. What you get is a slow push in. The same works for any animatable property: position, opacity, volume, blur, colour. Interpolation between markers is adjustable, and that is where most of the craft sits, because linear movement looks mechanical while easing in and out looks intentional. A second meaning causes constant confusion. In video compression, a keyframe or I-frame is a fully encoded frame that later frames are described against, and it has nothing to do with animation.