OK, here's hoping the responding posts will clear up my ignorance without too much ego-bashing.
First, I admit it. I'm an old fogey and I don't participate in online forums anywhere, but here, excluding work-related Intranets.
Therefore, with little such experience in this environment, I have been mystified trying to decipher the all pervasive concept of "IN", which I see referenced in many threads, and is frankly far beyond my current level of comprehension. I thought I had it figure awhile back, but as I continued to read and register its usage, the elusive thing seemed to morph in mid-post, corrupting my neatly arrayed premises supporting my definitive conclusion as to its nature, meaning and proper usage.
So my question is, what in the stunted domain of acronymic, grammatically-crippled, English-crushing online forum linguistical jargon does "IN" mean?
(Pleas ignore the redundant adjective in my last sentence. Sounded good so I left it that way on purpose.)
TEST: Can you identify the redundant adjective I refer to?
EXTRA CREDIT: What is the generally-accepted grammatical faux pas I just committed in the previous "TEST" sentence.