"Here's the thing" can be used as a buildup to an insult and to make sure you'll have the attention of the receiving party. Ending it with a "that's more or less the thing" will let them know that you've finished conveying this information.
Jack: My allegiance is to the law, I'm paid to uphold the law.
Bill: What in the heaven's name are you talking about? You may have misgivings, but don't go believing that, Jack. That way lies damnation.
Jack: I'm in no danger of damnation, Bill.
Bill: Here's the thing, I don't give tuppenny fuck about your moral conundrum you meat-headed shit sack, that's more or less the thing.
Some activity with some object that you can't or won't name because a) it's embarrassing b) it's too weird c) you don't know what it's called or d) it's just funnier like that.
Not infrequently used to refer to sexual activities.
Hey Hon, how about tonight you do that thing with the thing, you know, that I like so much?
A phrase often used when trying to explain why something is, isn't, needs to be, or just in general. This phrase often talks about an invisible or nonexistent object or "thing." Will often cause anger or laughter.
Guy 2: Hey why do these things run away when I get close.
A phrase used by Mira Suta to convey the message that her false fact is true using a series of other false facts.
Mira: Duck Hunt is really good. His side B is really powerful!
Mike: But he's low tier, and nobody likes him or uses him.
Mira: That's the thing! Nobody knows what to expect!