I'm confused by certain semantics regarding checks and counters. When browsing Victim Of The Week threads, I've seen people adding adjectives "hard" and "soft" to those two terms, and while each opening post provides commonly accepted definitions of the two general terms, I haven't seen a single definition of a soft/hard check/counter. Should I consider them cosmetic and ignore them, or are there set definitions for those posted somewhere I could be linked to? In case those terms are commonly used to describe an extent of mon's ability to check/counter another yet lack a commonly accepted definition, shouldn't official definitions be made for them?
Finally, what is the commonly accepted "room for error" for being a check or counter? Obviously we're not looking at exactly 100% surefire means of beating something, because otherwise M-Metagross wouldn't be even able to check anything with 90% accurate moves, for example. I'd guess the minimum allowed success chance of a given method of checking/countering would be something around 80%, but I want to ask to be sure.
EDIT One more thing. Do we always assume that Stealth Rocks are up on BOTH sides of the field, or only ours?