Traction is a measure of how far a character can slide on the ground, either by shielding an attack or by wavedashing. It is generally considered best for characters to have a moderately low traction, so they can wavedash an optimal distance.
This is a ranking of each character's traction, from least to greatest.
2) Ice Climbers
7-9) Dr. Mario/Mario/Mr. Game & Watch
15) Young Link
20-21) Captain Falcon/Kirby