What role does a keyframe play in animation?

A keyframe is an essential component in animation that specifies where change occurs, acting as a marker for important points in the timeline of an animated sequence. When animators create motion or transformations in their projects, they use keyframes to define the starting and ending states of an object or element. These keyframes provide context for the software to interpolate the movement or change between them, resulting in a smooth transition.

In the context of animation, keyframes are crucial for defining timing and the nature of the transitions between different animations or states. For example, if you want an object to move from point A to point B over a set duration, you would place keyframes at those points to indicate the positions and the software would calculate the in-between frames, known as inbetweens, to create fluid motion.

The other options do not accurately describe the primary function of keyframes. While transitions can occur between keyframes, it is the keyframes themselves that specifically denote where these changes happen within the animation. Similarly, they do not mark the commencement of the video nor are they directly responsible for reducing file size. Keyframes are inherently tied to the animation process and are integral to defining movement and transformations.