Learn Hardcore Indonesian: Guru kami memberi penjelasan mendalam tentang sejarah Indonesia. - Our teacher gives an in-depth explanation about Indonesian history.

kami = we (excluding the person being spoken to)
→ the listener is not included
kita = we (including the person being spoken to)
→ the listener is included

In Guru kami memberi penjelasan mendalam tentang sejarah Indonesia, kami usually implies:

our teacher (the teacher of our group, not including the listener)

If you said guru kita, it would mean:

our teacher where you and I (and possibly others) share this teacher.

So guru kami vs guru kita can subtly change who belongs to the group that “owns” the teacher.

Why is it guru kami and not kami guru for "our teacher"?

In Indonesian, the normal order is:

Noun + possessor

So:

guru kami = our teacher (literally: teacher we)
rumah saya = my house (literally: house I)
mobil mereka = their car (literally: car they)

Putting kami before guru (kami guru) is not standard for possession and would sound wrong in this context.
kami guru could only appear in a different structure, for example:

Kami guru di sekolah itu. = We are teachers at that school.

Here kami is the subject we, and guru is a predicate (are) teachers, not a possessive phrase.

What does memberi penjelasan literally mean, and can I just use menjelaskan instead?

Literally:

memberi = to give
penjelasan = an explanation

So memberi penjelasan = to give an explanation.

Yes, you can often replace it with menjelaskan, which means to explain:

Guru kami memberi penjelasan mendalam tentang sejarah Indonesia.
Guru kami menjelaskan sejarah Indonesia secara mendalam.

Both are natural; the nuance:

memberi penjelasan focuses on the act of giving an explanation (noun-based).
menjelaskan focuses on the verb “explain” directly.

They are both fine and commonly used. Your original sentence sounds slightly more formal or written.

Why is it penjelasan mendalam and not mendalam penjelasan?

In Indonesian, adjectives and many descriptive words usually come after the noun:

penjelasan mendalam = a deep explanation
buku tebal = a thick book
rumah besar = a big house

Putting mendalam before the noun (mendalam penjelasan) is ungrammatical.

Here penjelasan (explanation) is the noun, and mendalam (deep, in-depth) describes it, so:

penjelasan (noun) + mendalam (adjective)

Is mendalam an adjective or an adverb here? How is “deeply” expressed?

In penjelasan mendalam, mendalam works like an adjective: in-depth / deep.

If you switch to the verb menjelaskan, then you typically use secara mendalam to mean deeply / in depth:

Guru kami menjelaskan sejarah Indonesia secara mendalam.
= Our teacher explained Indonesian history in depth.

Pattern:

mendalam directly after a noun → adjective-like: penjelasan mendalam
secara mendalam after a verb → adverb-like: menjelaskan … secara mendalam

Could I say penjelasan yang mendalam instead of penjelasan mendalam? Is there a difference?

Yes, you can say both:

penjelasan mendalam
penjelasan yang mendalam

Both are grammatically correct and natural.

Nuance:

penjelasan mendalam is a bit shorter and more neutral.
penjelasan yang mendalam can feel slightly more emphatic, like “an explanation that is deep / truly in-depth”.

In everyday usage, they’re often interchangeable. Your original sentence is perfectly fine without yang.

What is the role of tentang in this sentence? Can it be omitted or replaced?

tentang means about / regarding / concerning.

In the sentence, it links the explanation to its topic:

penjelasan mendalam tentang sejarah Indonesia
= an in-depth explanation about Indonesian history

You can sometimes replace tentang with near-synonyms:

mengenai (about, regarding)
soal (about, regarding; more informal)

For example:

penjelasan mendalam mengenai sejarah Indonesia
penjelasan mendalam soal sejarah Indonesia (more casual)

In this sentence, tentang cannot just be omitted.
Without it, penjelasan mendalam sejarah Indonesia sounds incomplete or clumsy, because we need a clear marker that sejarah Indonesia is the topic.

Why is it sejarah Indonesia and not Indonesia sejarah?

The normal pattern in Indonesian for “X of Y” or “Y’s X” is:

Head noun + modifier

Here, sejarah (history) is the head noun, and Indonesia specifies whose history:

sejarah Indonesia = the history of Indonesia
sejarah Jepang = the history of Japan
sejarah keluarga = family history

So:

sejarah Indonesia (correct) = Indonesian history
Indonesia sejarah does not work as a noun phrase in standard Indonesian.

How do I know which noun is the “main” one in something like sejarah Indonesia?

In a basic Noun + Noun phrase in Indonesian:

The first noun is the main thing.
The second noun specifies or limits it.

So:

sejarah Indonesia
→ main: sejarah (history)
→ specifier: Indonesia (of Indonesia)

Other examples:

bahasa Indonesia = the Indonesian language
(main: language; specifier: Indonesia)
bendera Indonesia = the Indonesian flag
(main: flag; specifier: Indonesia)

So when you see Noun A + Noun B, think: “A of B” / “A related to B”, with A as the main noun.

What are the word roots and affixes in memberi, penjelasan, and mendalam?

Breaking them down:

memberi
- Root: beri = give
- Prefix: meN- (here realized as mem-) → forms an active verb
- memberi = to give
penjelasan
- Root: jelas = clear
- Prefix: peN- and suffix: -an
- menjelaskan = to make something clear, to explain
  (meN- + jelas + -kan)
- penjelasan = explanation (the noun form: “the act/result of explaining”)
mendalam
- Root: dalam = deep / inside
- Prefix: meN- (here men-) → mendalam can mean to deepen, but it is also used as an adjective meaning deep / in-depth in many contexts (like in your sentence).

So the sentence uses several common Indonesian affix patterns that turn roots into verbs and nouns.

How formal is this sentence, and can it be used in everyday spoken Indonesian?

The sentence is neutral to slightly formal, mainly because of:

memberi penjelasan mendalam (a bit more “textbook”/written style)

It is still completely natural in spoken Indonesian, especially:

in a school or university context,
when talking about what a teacher did in class,
or in a slightly careful or polite conversation.

In more casual speech, someone might shorten or simplify it, for example:

Guru kami jelasin sejarah Indonesia dengan sangat mendalam.
(colloquial: jelasin instead of menjelaskan, and dengan sangat mendalam as another way to say “very in-depth”.)