From the Super Mario Wiki
A checkpoint warp is an object that appears in Yoshi Topsy-Turvy. It appears as a ring made out of big and small yellow stars that slowly rotates. When Yoshi touches the checkpoint it will disappear into an explosion of confetti and sparkles and will warp Yoshi to the next area of the mission. They appear in every area of each mission except for the last area, where the Goal replaces it. A large amount of checkpoint warps may appear at the bottom of certain stages.