What difference does level make

In Super Smash Bros Melee, a character can wavedash by doing a diagonal downward air dodge when just above a platform. This causes the character to slide along the platform in the direction of the dodge. Players often accomplish this by doing a short hop and then immediately dodging in the desired direction.

This move is very difficult to pull off consistently, but players who can do it will sometimes use it instead of a roll. Wavedashes are often better than rolls because there are fewer recovery frames, or frames when the character is vulnerable between the part of the dodge when the character is invincible and when the character can do anything else.

This move is an unintentional side effect of interactions between different parts of the physics engine, and was not even discovered for years after the game came out. You can not wavedash in Brawl simply because it has a different physics engine. In particular, air dodging works differently in Brawl.

Float-cancelling is a technique/exploit/glitch/bug/etc where, if Peach is floating when she uses an aerial attack, she does not go through the attack's landing lag if she hits the ground during the attack. Generally this is done by floating into an incline to land. Since normal landings are even faster than L-cancelled landings, this basically lets the player do things faster.