Spin jump
The "spin jump" is a move that can be performed by Mario, Luigi and Toad.
History
The spin jump first appeared in Super Mario World, where Mario could perform the move once he was in his "super" form. Since then, it has appeared in many games, most notably in Super Mario World and the console releases of the New Super Mario Bros. series (starting with New Super Mario Bros. Wii). The move has also been featured in various RPG-games within the Mario franchise.
The various iterations (excluding the ones in the RPGs) function more or less the same though.
In Super Mario Bros. X
In Super Mario Bros. X, the move works exactly the same as in Super Mario World.
If you are playing as either Toad, Mario or Luigi and you're also in their big form, they can break certain blocks by spin jumping on them. When they're small, this won't work however. The spin jump also protects against some enemies, like Spineys, when you land on them.
However, the spin jump looses momentum and has a lower jump height than the regular jump. In addition, you also can't propel yourself high into the air by stomping on enemies.