Adding to the above things, it also encompasses things like T-Wave, Trick Room and Sticky Web if you wanted to be petty about including everything, which can slow fastmons down to a point where they are manageable (tho Webs is pretty worthless atm 'cuz most scarfless fastmons either carry Boots or are immune regardless/not prone to being Knocked) as well as WeatherSpeed 'mons, Hawlucha, and I guess Tailwind if you want to be petty about including everything that let you beat them situationally (Sand often doesn't have much speed control beyond Excadrill/Dracozolt, for instance, and Hawlucha is the whole reason HO can compete vs a lot of naturally fast 'mons and Scarf users). The general idea is just ways of moving first vs fastmons and (typically +1 Spe) setup sweepers without the attacker first needing to take a hit to attack or set itself up.