These three get mixed up, and each suits a different clip:
Reverse
The clip plays backwards once, from the last frame to the first. Use it for magic-trick edits (a jump out of a pool, a cup un-spilling), or to fix footage that was recorded in the wrong direction.
Boomerang
A short moment plays forwards and then backwards, on a loop. Choose Boomerang under Make for that, or read how to make a boomerang from a video.
Rewind effect
The clip plays normally, then whips back fast, often with tape lines. That’s the Rewind style of a boomerang: it returns at 2.5× with scan lines and a rewind badge.