Speed
Who moves before a chosen Pokemon
How speeds are compared
Pick a Pokémon and you get its Speed under four spreads: no IVs or EVs with a hindering nature, 31 IVs and 0 EVs, 252 EVs on a neutral nature, and fully maxed. Everything uses the level set at the top, 50 for VGC or 100 for Smogon singles, and the Pokémon stays in the link so you can share it.
The comparison maxes out both sides, 252 EVs and a boosting nature, because pitting your best case against everyone else's worst would give a comfortable list that never holds in a real battle. It tells you how many are faster, how many are slower and how many tie, which turns move order into a coin flip, and lists the 15 closest on each side.