The Tetris action that increases a piece’s downward speed without instantly placing it is soft drop.
Soft drop lets players accelerate a falling tetromino while retaining control over its horizontal position and rotation. The piece continues falling under player control, rather than immediately snapping into its final position.
This is different from a hard drop, which places the tetromino instantly at the lowest available position. A wall kick is a rotation-system adjustment that can move a piece around an obstruction, while lock delay is the brief period before a landed piece becomes fixed.
Soft drop is useful for speeding up play, setting up precise placements, and earning points in many modern Tetris versions. The feature was not present in every early release; it became part of later standardized Tetris guidelines, including The New Tetris in 1999.