What does ~는 것 mean?

See a translation

Quoted from https://www.koreanclass101.com/forum/viewtopic....

Let's Break --는 것
First, Here, --"는" is sort of usage of "to verb" or "V+--ing".
For examples,
보다 "see" becomes 보 (verb-stem) + 는 = 보는 (seeing, to see)
하다 "do" becomes 하 (verb-stem) + 는 = 하는 (doing, to do)
먹다 "eat" becomes 먹 (verb-stem) + 는 = 먹는 (eating, to eat)
배우다 "learn" becomes 배우 (verb-stem) + 는 = 배우는 (learning, to learn)

Now, let's take a look at "것".
"것" is 'Possessive Pronoun' that attaches to 'adjective' or 'Verb + -ing' (most times) and help the phrase to become NOUN.
Remember this - in the sentence, A is B, A must be NOUN or Noun phrase.

"Seeing is believing" = 보는 ("seeing" - adjective) + 이다 ("is" - verb) + 믿는 ("believing" - adjective)
If I literally translate it, "Seeing is believing" becomes 보는 믿는 이다, which is NOT a Korean sentence at all.
HOWEVER, you can make it correct by attaching 것 right after 'Verb+ing' and, it becomes NOUN!!!

보는 "seeing" + 것 "possessive pronoun" = 보는 것 (FINALLY "seeing" becomes NOUN) in Korean.

Okay, I hope now you understood some of this grammar rule.
Okay, go back to "Seeing is believing" = (literal translation) is 보는 믿는 이다.
Now you know how to make 'Verb+ing' into NOUN by attaching 것.
"Seeing" 보는 + 것 "Possessive Pronoun" = 보는 것 "seeing (NOUN)"
"Believing" 믿는 + 것 = 믿는 것 "believing (NOUN)"
Finally, the correct translation for "seeing is believing" is 보는 것 + 은(Topic Marking Particle) 믿는 것 이다.
보는 것은 믿는 것이다. "seeing is believing"
"Doing is necessary" 하는 것은 필요하다.
"Eating is essential" 먹는 것은 필수적이다.
"Learning Korean is my dream" 한국어를 배우는 것은 + "learning Korean" 내 꿈 + "my dream" 이다 "is"
=한국어를 배우는 것은 내 꿈이다.
Same thing with "My dream is to learn Korean." = 내 꿈은 "my dream" + 한국어를 배우는 것 "learning Korean" + 이다 "is"
=내 꿈은 한국어를 배우는 것이다.