It joins two talking shots made from nearly the same position so a skipped moment seems to melt together. The face or expression may briefly warp.
Join similarly framed clips and apply a morph correction offered by some editing tools. It estimates motion between frames and interpolates them, so choose an edit where faces and hands do not overlap awkwardly.
Morph cut is a feature name in some editing tools, and naming or support varies by tool. If the background or subject changes too much, distortion becomes obvious; use a short dissolve or leave the jump instead.
When to use
Try it when trimming a talking shot but softening the visual jump. If the face or background bends, remove the correction.