Animation crossfade
Sliding smoothly from one animation clip to another by blending the poses over a short window, instead of a hard cut that makes the character "pop".
Switch clips outright and the skeleton jumps from the last pose of one to the first pose of the next — a visible snap. A crossfade interpolates between the two poses over a transition time, typically 0.1–0.3 seconds, so the motion flows. It is the same idea as an audio or video crossfade, but applied to bone rotations.
Fail to match the clips' speed and footfall and the feet slide ("foot sliding") during the blend — a classic artefact. Crossfades are built into every animation state machine and are a form of animation blending confined to the moment of transition.