Define object position, rotation, or properties at specific frames — software interpolates the in-betweens. Foundation of all digital animation, from motion graphics to VFX.
You set a keyframe and define an exact state with it — position, rotation, scale, opacity, whatever. The next keyframe two seconds later with a different value. The software calculates everything in between for you. That's the foundation. Nothing works in digital animation without keyframes, whether you're doing motion graphics, character animation, or controlling particle effects.
In practice, you always set keyframes where something is supposed to change — not continuously, but at the crucial points. A camera panning from object A to object B? Keyframe at position A, keyframe at position B. The system interpolates everything in between linearly, or — if you want — with smooth curves (ease-in/ease-out). That's the key advantage: you don't need to draw or set every single frame. You only define the control points.
The interpolation between keyframes is the critical detail. Linear interpolation creates sharp, mechanical movements — practically never what you want. That's why you almost always use spline interpolation or Bezier-based curves. On set and in VFX workflows, this allows you to realistically accelerate or decelerate movements. A door doesn't slam shut linearly; it accelerates and brakes. Keyframe animation makes this possible without you fiddling frame by frame.
In modern software packages — be it After Effects, Cinema 4D, Houdini, or Unreal — you work with a keyframe timeline. You see all keyframes on a ruler, can move them, change their value, adjust their interpolation curve. This has been standard for decades, and there's no reason to change it. The only pitfall: too many keyframes make the curve wild and unpredictable. Less is more. Set keyframes precisely and trust the interpolation.
Cross-reference: The concept overlaps with motion capture (when you digitize real movement) and procedural animation (when algorithms calculate the keyframes), but keyframe animation is the manual, craft-based counterpart — you have control.