It's, My Old Nemesis - The Comma Is Deliberate

I've already gone on about the peculiarity of idioms and spelling rules, and now I've got to admit that some grammatical rules are just plain stupid.  No better example exists than the conjugations of "it," which, unfortunately, seem pretty inevitable in writing and the guidelines of which are so baffling that I regularly confuse myself in attempting to explain them*.  Thus, for my own sake as much as anyone else's, let's start with the basics.

Okay, so, here we go: "it" is a pronoun, which stands in for a noun, freeing you from the necessity to repeat that noun every time you reference it.  See? Without pronouns, that would have been "repeat that noun every time you reference that noun." Pronouns are handy.

Now then, most pronouns have conjugations all their own, because they're special snowflakes and think they're verbs or something.  You've got "their," for something that belongs to multiple people - e.g., "Those are my neighbours, and that's their spaceship."  There's also "her," "his," and "my," for the possessions of your sister, your brother, and yourself.

This grants suffixes freedom to do their suffix thing.  They're, she's, he's, I'm - to append "to be" to most pronouns is an easy proposition.

It, on the other hand, doesn't conjugate like other pronouns.  It is just it.  Maybe that's because it only has two letters, but English usually doesn't let little things like logic stop it so honestly I have no idea.  Nonetheless, there it is - pun intended, if that's even a pun.

Anyway.

The thing to bear in mind is that "it"...okay.  I had some kind of logical key a second ago and then I realised that it was bass-ackwards and I'd gone and baffled myself with the conjugation of "it" again.  Sans further prevarication: "it's," despite the possessive form of pretty much every non-pronoun word in the English language forming with the addition of an " 's," means "it is."  It's is "it is."

"Its," on the nonexistant third hand, means "belonging to it."  I keep trying to come up with some sensible explanation for this, but I begin to doubt there is one.  "It" is just a stupid, stupid word, on idiotic par with people who keep trying to impose sense on its vagaries.  You just have to memorise it.

*I've mentioned my gift for spelling, right?  Well, I'm not the only one who's noticed; since early childhood, people pushed me to enter spelling bees while I, being part goat or something, resisted more the harder they pushed.  Mum finally succeeded sometime in my tenth year and I promptly got kicked off the first round for spelling the wrong version of "it."