Differences between 그거, 그건 and 그게
What is the difference between these? In my book, they don't emphasize the difference of 그거 from 그건 and 그게; however, they do tell that 그건 (short for 그것은) is used when you want to 그것 as a sentence topic, point up a contrast, or mark it as old information and that 그게 (short for 그것이) is used when you want to put a spotlight on 그것.

Yesterday, I was told that the difference lies on the formality of the conversation; in other words, the relationship between you and the person you are talking to, which totally confuses me because my book doesn't mention that anywhere.

If it helps, I am using Elementary Korean (Second Edition) and I am in Lesson 5.

Thanks for your time,
mxWhat I am actually looking for is the usage of 그거. I know what the differences between 그건 and 그게, but how would 그거 be different from those two?

Question

Differences between 그거, 그건 and 그게
What is the difference between these? In my book, they don't emphasize the difference of 그거 from 그건 and 그게; however, they do tell that 그건 (short for 그것은) is used when you want to 그것 as a sentence topic, point up a contrast, or mark it as old information and that 그게 (short for 그것이) is used when you want to put a spotlight on 그것.

Yesterday, I was told that the difference lies on the formality of the conversation; in other words, the relationship between you and the person you are talking to, which totally confuses me because my book doesn't mention that anywhere.

If it helps, I am using Elementary Korean (Second Edition) and I am in Lesson 5.

Thanks for your time,
mxWhat I am actually looking for is the usage of 그거. I know what the differences between 그건 and 그게, but how would 그거 be different from those two?

Answer

I answer again.

I think you might misunderstand.
You said "그건 (short for 그것은) is used when you want to 그것 as a sentence topic,..."
and " 그게 (short for 그것이) is used when you want to put a spotlight on 그것.". 

-> You're right. The subjective particles 은,는/이,가 enable what you said. In other words, the meaning of the words rely on the particles. So it is matter of the use of 은,는/이,가.

However, you said "...the difference lies on the formality of the conversation..." is incorrect. In informal conversation(in spoken language), we use 그건, 그게, 이건, 이게 instead of 그것은, 그것이, 이것은, 이것이.

Answer

I understand it's a qusetion about the subject particles 은,는/이,가. 
그것은=그건, 그것이=그게 
Jhon 존은, 존이

OK. Go to the site below, it will help you;
http://123learnkorean.com/korean-grammar-bank/korean-grammar/particles-%EB%8A%94-%EA%B0%80/

Answer

What does the grammar mean in the sentence? https://bestdoctornearme.com/
I have a few questions. What does mean? I don't understand what the grammar point sleep means in this sentence. Why wasn't if alone used?

Answer

As far as I know, 그것은 and 그것이 in more formal settings and in writing. I don't hear them a lot in casual speech.

The difference between 그거, 그건 and 그게 has to do with the particles 은/는 and 이/가.

Listen to this lesson.
http://www.talktomeinkorean.com/lessons/l1l9/