Let's Get the Basics Out of the Way

My sickness here goes much deeper than the ubiquitous you’re versus your, it’s and its, and there, they're, their. Those writers just need to go back to elementary school. I mean, come on. It's not that hard. However, just for the record, let's get the basics out of the way.
 
The apostrophe is used to mark omissions and possessives of nouns and pronouns. I know: That one sentence made me sound like a dork. Guess what? I don't care. I embraced my inner dork a long time ago. But here. Let me explain: A noun is a person, place or thing. A pronoun substitutes for a noun. Here's an example: "Sharon is a word nerd. She embraces it." In these sentences, Sharon and nerd are the nouns, and She and it are the pronouns. Can we move on now?
 
Let's deal with omissions first. I'm talking about contractions here. Please tell me you know what a contraction is. It's a shortened form of a word. It's a word that got rear-ended and a letter popped out: it's, don't, can't, you'll, whate'er. (I hate that last one, by the way, and not for any good reason. It's just annoying.) Anyway, in a contraction, an apostrophe indicates that a word or part of a word is missing: it's is missing the i from is, and they're is missing the a from are. Just think of that little apostrophe as a placeholder. The little bugger broke in line and is holding a spot for his missing letter friend.
 
Now, let's move on to apostrophes used for possessive nouns and pronouns. Possessive in this case doesn't mean the words are greedy. It means they own something. So in this sentence -- "Sharon's AP Stylebook looks like it's seen better days." -- the first apostrophe is possessive. I own that stylebook. Yes, ma'am. I really do. (And that apostrophe replaces the d in madam. I know. I just blew your mind, right? You're welcome.) The second apostrophe is for a contraction in which the a in has has gone missing. 
 
So stop using that tiny apostrophe to try to kill me. Don't use him when the word you're jamming him into is neither a contraction nor a possessive word. I can feel myself dying a little when I see your beautiful Christmas cards with lovely pictures of your beautiful children -- and then you sign it like this: Merry Christmas from the Smith's. No, ma'am! Well, unless you're really the Smith Is family. Then I could let that one go.