Classification Confusion in English

I want to learn English grammar but I am confused. For example, everyone talks about relative clause and noun clause, but basically they don't talk about what "that" means. They don't mention the difference between the "markers" that are common in the relative pronoun and noun clause structure.

There is a class called subordinating clause. This includes relative clause, but there are no relative pronouns in the list of subordinating conjuctions!

I know that your name is Angela Merkel.
I like cats that sleep quietly.

These two have "that" in them. One of these sentences is an adjective clause and the other is a noun clause. But what they have in common is "that" and nobody is interested in the specific question "What is that?".

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I will ask something in addition. Is the following completely true (probably yes). So, are all subordinating conjunctions also conjunctions?
2 months ago I started learning grammar, I didn't even know what an adverb was. It is very difficult to find grammar answers that are not superficial.

There are many errors in the layout of your tree; too many to quickly list.

You can't learn grammar overnight. I suggest that you buy a textbook based on modern descriptive grammar and start from the beginning.

I need to get out more. I have never noticed that everyone talks about relative clauses and noun clauses.

I suggest that you arrange your posts so that after one paragraph you are finished.

The word "that" is used quite often, and that is all I have to say about that for now.

I suggest that you decide what question you want to ask and then ask it.

Tarheel said:

I suggest that you decide what question you want to ask and then ask it.

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Soldierman mentioned several problems they faced. This was perfectly reasonable, though beyond the scope of this forum.

Hello @soldierman034 and welcome to the forum. We ask members for their mother tongue because long experience has shown that we can better help learners if we have that information. Please correct the Native Language field in your profile.

I think that's pretty much true. Almost nobody is interested in what "that" is.