From Sonic Retro
The Top (コマ) is an item found in Sonic the Hedgehog 3's Marble Garden Zone. By standing on one and holding left or right, Sonic will move in that direction while gaining altitude—likewise, to lower Sonic, the player must merely not press any directional buttons. If Sonic is hit while standing on a Top, he will only be knocked off the Top without losing rings or a life, although he will lose his shield if he possesses one. If Sonic jumps while on a Top, he will lose that Top and be unable to use it again.
The spinning Top's main use is to break down walls in the Marble Garden Zone that would normally be unbreakable using Sonic's Spin Dash or Knuckles' fists. To use it, the player must land the Top on the ground in the wall's vicinity; the Top will speed off in the direction Sonic is facing, breaking through any walls in the way. In addition, the Top can also be used to break floor sections in order to reach lower areas. Breakable floors look very different to standard floors, and so are easy to identify. Tops can also be used to travel at high speed along the ground and around large pillars. This can be done either by forcing a Top to land, or standing on a Top which is already on the floor.
It's also possible to land one Top on top of another. When this happens the Top Sonic is standing on will move in the direction Sonic is facing, but at an extremely slow speed.