The basic meaning is stated above (it conceptualizes whatever the subject is, which seems pretty intuitive since it’s literally “the thing called____”), but be careful of とういうこと appearing in unexpected places in a sentence and in front of certain particles, as it can take on other meanings. Ex. とういうことは at the beginning of a sentence is equivalent to “in other words/which is to say,” while とういうことで means “therefore,” building off a reason or impetus in the previous sentence.
And separately but relatedly, というのは is a phrase that precedes reasons/explanations. “That’s because…”
This is usually covered in N2/upper-intermediate study, so don’t feel like you need to actively remember anything other than that basic meaning right away, but maybe keep those in mind if they pop during reading. They all kind of make sense, in a way, but can be hard to keep track of.
EDIT – For the difference between こと and とういうこと, look at your examples again. こと only follows verbs above, whereas とういうこと follows a noun. This is because, while とういうこと conceptualizes (so it can follow verbs and adjectives, but then you’re talking about the word as a word/concept), one of こと’s major functions is to nominalize. You’re probably already familiar with this, but like, 読む (to read) and 読むこと (reading, as a noun). And then you could theoretically have 読むとういうこと (the thing that is reading/reading, reading as a concept rather than an action) as well, just to drive that difference home.
But こと also has a bunch of other roles, and one of them is in your first and third example sentences. ～ことになる means “to be decided that～.” So your first sentence is, “I wonder if that husband and wife will decide to split up in the end.” (The whole sentence is actually intransitive, but that doesn’t carry into English translations well.) Your bottom one is “It was decided that the meeting would be postponed,” or to get a more natural translation, “The meeting was postponed.”
And のこと can also follow nouns to mean “about/regarding” whatever. Ex.) あの、会議のことですが… “Um, about the meeting…” 私のことですか。 “Are you talking about me?”
And even more. こと does everything, but you can generally navigate what’s happening in new constructions if you remember it’s “thing.” “About this thing,” “this thing has been decided,” “～ing (as a nonconceptual thing),” etc.
(というもの exists too, as an emphasizer, so have fun with that.)