The way they've been used so far:
A soft check is something that can't switch in, or can only switch in on one or two moves, usually moves that aren't spammed. An example would be ScarfChomp for ScarfKyu-B. Garchomp can take an Earth Power, a Fusion Bolt, an Iron Head, or a Hidden Power Fire on the switch with ease, and can OHKO Kyu-B. Its flaws though are obvious, since if it switches in on Substitute, Outrage, Dragon Claw, or Ice Beam, it's doomed.
A hard check is something that is almost a counter, but fails for some reason(s). One example I remember was Rohail's nomination of Alomomola as a hard check for bulky-dd Charizard-X. The reason it was a check and not a counter is because while it walls it at +1, it has no offensive presence and is thus setup bait. Toxic will wear Charizard down, but if fishy can't threaten it as much as say Quagsire or Rhyperior can.
A soft counter is something like Zapdos for Pinsir. Zapdos is always 2HKOd when Pinsir is at +2, but always OHKOs, is never OHKOd, even after rocks, and has recovery to help it.
A hard counter is obvious; something like Quagsire for Mega Scizor.
idk if these are official or anything - they're just what we've been using so far :)
Just gonna post
this funny replay I had to affirm this; Rhyperior is amazing.
Okay. I added all of the mon's sets to the archive, and when I have like 30 mins or so I'll add their descriptions.
Anyway the c&cs look great so far! Don't forget to add some sets to the archive, like
linkinparkrules has done with his great Heracross nomination!