DnD is just a rule base to create your own fantasy settings within. The different official settings are there for people not interested in creating their own world. Each and everyone is basically a self contained universe.

Elminster is Gandalf, that's enough for me:)

Erevis Cale, a rogue/fighter/cleric/divine agent shade, chosen of mask, and Jordain Matteo, a magic resistant (or magic immune) spellcaster. Both important for different reasons, unsure how well known they are though. May also add Liriel Baenre and Fyodor since their actions also caused changes to the Realms.
And I still have a ton of books to go through.

Forgotten Realms lore is very similar to Warhammer lore in that there's a whole lot of people writing stories and, as far as WotC are concerned, they are all canon. If I remember right, when Eberron came out they declared that the books weren't canon specifically to avoid the clutter that occurred in the Forgotten Realms after 30 years.

Anyway, I never made the jump to 4th of 5th Editions, so my knowledge is a little out of date. Ed Greenwood made the Forgotten Realms, and Elminster is his pet character. As noted above, he's basically Gandalf. In 3rd Edition, the biggest event was the Time of Troubles, used to explain the changeover from 1st Edition to 2nd Edition AD&D. In that, the overgod Ao got pissed at the gods and forced them to take mortal forms and sent them to the Realms. This is where the story of Baldur's Gate comes into play, as Bhaal died during the Time of Troubles and someone else had to take up his divinity.

I think I heard that in the changeover from 3rd Edition to 4th there was something that made it kinda post-apocalyptic? Where basically everything outside the cities got super fucked up and now the countryside is way more dangerous than it was in 3rd.

Part of the problem with explaining lore too is that the Forgotten Realms are really, really huge. The areas that you know from the Baldur's Gate/Icewind Dale/Neverwinter Nights are a tiny, tiny portion of the map, and there are other campaign settings that are set on the same world (Blood and Magic, that early D&D RTS, is set in one of these areas).

When did the Forgotten Realms take over the generic setting from Greyhawk?

I'll second what Mich has said. Perhaps a better comparison would be asking what's the lore of fantasy novels. There is no one world, no one setting, no one set of characters.

Even if you limit yourself just to the Forgotten Realms universe, you have to ask which continent, which region, which people, which time period. There is no single story with just a dozen main characters of any importance, like you might find in LOTR or King Arthur.

As others have explained, D&D is NOT a single region, or world, or universe. D&D is a rule system by which you can make your own world and story. Most stories have centered on standard medieval fantasy settings, but there are plenty of others, such as asian settings, african, desert planets, space travel, fantasy worlds with a race of sentient [s]robots[/s] golems... D&D is just the rules framework for whatever setting you want. IIRC Kotor 1 used the D&D rules (D20)... would D&D lore include that, or would it be considered star wars lore?

You really have to narrow your question down to get a meaningful response. "What's the lore of D&D" is both impossibly broad and also nonsensical. If you're asking about a specific video game, like BG or NWN, I think you'd get a much better response saying so.

In a nutshell, FR has hundreds of gods spread over dozens of pantheons. Each god has a few mortals given major blessings, called "Chosen of _________". Elminster for example, is a Chosen of Mystra, human goddess of magic. Being a Chosen basically makes you a rules-breaking overpowered munchkin mary sue. At one point all the gods were stripped of most of their power and cast down amongst the mortals by Ao the Overgod. This was called the Time of Troubles. A few gods died, but eventually Ao let all the gods return, and it's right after this time that BG is set (Bhaal, god of murder, was one of the gods who died).

[url=http://forgottenrealms.wikia.com/wiki/Portal:Deities]List of some FR gods, scroll down, left hand side[/url]

Most of the areas where gameplay occurs in FR has moved from feudal kingdoms to city-states. The cities of Neverwinter and Baldur's Gate are both city-states. Humans are the vast majority, as elves have withdrawn across the ocean, dwarves are underground, and gnomes and halflings live far, far to the south.

There are some large factions in FR, the Harpers and Zhentarim mentioned in those two games. Basically, the Harpers are a secretive group of "good" guys, while the Zhents are a secretive group of "bad" guys. Jaheira and Khalid are Harpers, Elminster is one of the leaders (finger in every pot), while Xzar and Monty are Zhents.

summary of some FR factions

HTH

not sure why you think making a thread is going to get you more than, ya know, actually looking stuff up and reading it will

See, that's the kind of stuff that makes said settings "not D&D".

D&D the game is a game about exponential advancement, and the stories it generates are about, duh, exponential advancement. So the heroes of D&D stories don't interact (or do interact and hate it, if your DM is terrible) with DM penis npcs; your questgivers and your notable enemies are roughly the same level as yourself and they're disposable. Meanwhile, the interesting characters from novels are interesting precisely because they star in coherent stories where cause and effect are still a thing, and because Wizards want to capitalize on these occasional successes, the characters don't advance and thus stay out of the D&D framework.

If there are any iconic D&D characters, they're the characters of Gary Gygax's group that made it into official supplements, however strange it may sound. Even though they're all Very Fucking Old [tm] irl, they're not so much ossified as frozen in time, and the protagonists of D&D stories can have meaningful interactions with them (including killing them and stealing their stuff).

Exactly. The lore of D&D is what you make it. D&D is a ruleset, a platform, for making your own world.

And why isn't Australia in Europe?

Because Dragonlance is it's own setting. Toril and Krynn don't coexist in the same place. As well ask why Final Fantasy games don't have any literary consistency between games, or why none of their characters or stories are included in the Forgotten Realms.

Honestly just deep dive on some wikis man, it's much better and faster than a forum discussion.

"Ready Player One" has a lot of D&D stuff in it. Of course, that book has a little of everything in it.

well they probably already KNOW about the lore and are TALKING about it, not giving a virgin lessons

you really don't make any sense asking this here

go lookup and read things, it'll will be much better
^

Find the (rule)books for Ravenloft and Planescape, and read fluff from those. You can safely ignore the rest.