Sega's arcade version of Tetris was the dominant version of Tetris in Japan, and as such most Tetris clones and variants followed it's formula. Versions of Tetris based on Sega's have a ruleset that makes it feel different from versions released by Nintendo or other versions licensed by The Tetris Company. Fans of Tetris call this ruleset Sega Rotation to compare it with "Nintendo Rotation" (from the NES and GB games) or "Super Rotation" (the current-day Tetris rules).
(Currently stoled/copypastaed from [Tetris Wiki]
Games using TGM/Sega rotation generally uses the following color scheme:
Tetrominoes start out centered, rounding to the left. I goes in columns 3–6 counting from the left, O in columns 4–5, and others in columns 4–6. Each tetromino starts with its topmost solid block in row 20 (or 22 in TGM ACE). Each tetromino is ordinarily spawned flat side up. There is no initial rotation, and no wallkicks. Additionally, the ceiling blocks rotation.
Apart from I and O, all tetrominoes rotate such that the bottom of the tetromino is at the bottom of the piece's bounding box. S and Z rotate between two states so that the center column stays constant. O does not rotate; I rotates between two states as depicted in the illustration.
The differences between Sega rotation and Nintendo Rotation System are that the flat-side-down states of J, L, and T are pushed down by one space, that S and Z round in different directions, that I rounds differently from the other pieces, and that I requires more space under it to rotate to a vertical orientation.
Sega rotation originally used no wall kicks. Arika took Sega rotation, added mild wall kicks and initial rotation, and ended up with TGM Rotation, or Arika Rotation System. In addition to the TGM series, most arcade games developed in Japan before the guideline followed the Sega rotation rules with varying degrees of wall kicks, such as Flash Point, Bloxeed, Sega Tetris, and the Tetris Plus series.