A skid is a single-deck loading platform, and a pallet has both top and bottom decks. The pallet has a deck that rests on the floor, and the skid simply rests on pedestals attached to the deck.
The skid was the precursor to the pallet, and it gained popularity due to its usefulness in moving inventory. Evolving over time, pallets became the standard due to the stability provided by a top and bottom deck. There are two types of pallet construction: the stinger pallet and the block pallet. The block pallet can be entered from all sides like the skid, whereas the stinger cannot.