Keyframes are specific points in time used in animation and video editing to define the start and end of a transition or movement. They allow creators to set parameters, such as position, scale, or opacity, at these points, enabling smooth changes over time. By placing keyframes at different intervals, animators can create dynamic sequences that enhance storytelling. In software like Adobe After Effects or Blender, keyframes are essential for controlling animations. When a keyframe is set, the software automatically calculates the intermediate frames, known as in-betweens, to create fluid motion. This technique is widely used in both 2D and 3D animation.