The Superslide is the fastest known method of travel in the game next to HESS, so it is a highly desired trick for speedruns. Because of its speed, hover boots can be equipped after starting a superslide to hover over large gaps. It is also fast enough to clip through some areas, such as the Deku Tree as Adult. In addition, a superslide can be used to skip certain cutscenes, such as the owl texts. There can be odd effects when holding a superslide through cutscenes, and even allows you to keep the Master Sword in the Ganon cutscene.
A Superslide is set up similar to a ground jump; however, the timing is more precise. The easy, automatic way is to cast Nayru's Love, and then set up a Ground Jump. After you are hit by the damage (bomb, enemy, etc.), instead of storing the jump you will do a superslide.
Another method to set up a superslide using a bomb:
It's worth noting that it's fine for Child Link to instant shield drop for a 1 bomb slide, but for Adult Link doing it like this will hinder the frame leniency. Only the 1st roll frame will work well, while the next 2 will almost never work, and the 4th will never work at all. Awhile back, this was the standard method, but with time we have figured out that instant shield drop is bad for Adult Link superslides.
The timing for the mashed roll is a little precise and requires practice in order to become consistent at it. With enough practice you should be able to superslide in this manner with a 50%-90% success rate.
The frame data for Adult slides can be seen here
Superslides can be done without bombs. You just need another grabbable object and another source of damage. The grabbable object can be bushes, pots, bomb flowers, etc. The damage can be most enemy attacks, ones that don't knock Link over and his shield will block. Now stand in front of the grabbable object, and hold Z and R. The trick is to roll forward, and just as Link is about to finish his roll, have the enemy attack him and he will block it with his shield. If done correctly, Link will block the attack, but will be shot backwards at a great speed, and will still have the A button say Grab. Again you can keep the superslide as long as you hold R.
If the object you are interacting with is something that Link cannot pick up, such as bomb flowers or grass before you get a strength upgrade, it is possible to do what is called a superslide teleport.
In order to do this, first get a typical superslide off one of these objects. Note that it must not break in an explosion; the original object must still be intact so you can grab it, so if you use bombs or bombchus be careful of the set up. After getting the superslide and being shot back, let go of R, and you will be shot back to grab the object. Link will grunt and won't be able to pick it up. Note that if you superslide too far you will no longer be able to teleport back to the object.
The trick is useful however, because of one extra characteristic: When you warp back to the object, the Z position of Link does not change from where he teleported from. This means that if you superslide up a hill or slope and then warp back, you will be over top of the object you are trying to grab, and if you performed ISG beforehand you will stay there in the air. This is useful in some cases to get Shadow Temple Early. Additionally, if you go down a slope and warp back, you will be out of bounds below the object. This can be useful in certain situations as well, especially where there is out of bounds water to swim in.