In Super Mario World, Mario falls slower through the air if you are holding the jump button while he is falling. This applies to both the normal and spin jumps. A regrab is a jump where you do a less than maximum height jump, letting go of the jump button, then regrab the jump button again in midair, causing Mario to begin falling slower. This allows Mario to gain more distance with his jump while gaining less height. This is ideal in situations with low ceilings. Additionally, you can do a regrab after bouncing off an enemy. You do this by landing on an enemy without holding the jump button, getting a small bounce. Then, after you bounce off the enemy, you repress the jump button, getting more horizontal difference on your bounce without getting a high bounce. Both of these techniques are utilized heavily in Kaizo hacks in order to navigate longer gaps with lower ceilings.
Pressor to jump the appropriate height, then let go of the jump button. Then, in midair, re-hold the appropriate jump button to fall slower while moving right or left to cover a greater distance.