means In design and layout, the empty space added inside an element's edges, between its content and its border, to keep things from feeling cramped.

from From 'pad,' a soft cushioning material, whose own origins are murky — possibly related to a Low German or dialectal word for the sole of the foot or a soft lump. By the time 'pad' meant 'to stuff with soft filling,' 'padding' followed naturally: first the literal fluff in cushions and quilts, then figuratively the filler in a bloated essay or speech, and finally the breathing-room spacing of digital design.