Learn Hardcore Indonesian: Iklan itu tentang kebun binatang.

Putting itu before the noun (itu iklan) is also possible, but then it usually acts more like “that is an ad” or “that ad” in a pointing/contextual sense, not as a simple noun phrase. The default, neutral way to say that/the advertisement is iklan itu.

Does iklan itu mean that advertisement or the advertisement?

It can mean either, depending on context.

As “that advertisement”, it can refer to a specific ad you’ve just seen or are pointing at.
As “the advertisement”, it can simply mean a specific ad already known in the conversation (even if you’re not contrasting it with another one).

Indonesian does not have separate words for a / an / the. Often:

iklan = an advertisement / advertisements (general or indefinite)
iklan itu = that advertisement / the advertisement (specific, known, or being pointed out)

Could I say Iklan ini tentang kebun binatang instead? What’s the difference between ini and itu here?

Yes, Iklan ini tentang kebun binatang is correct. The difference is mainly distance (physical or mental):

iklan ini = this advertisement (close to the speaker, on the screen right in front of you, the one you just made, etc.)
iklan itu = that/the advertisement (a bit more distant, or one already mentioned earlier, or assumed known)

In many real situations, itu is also used like English “the” for something both people already know about, even if it’s not physically far away.

Why is there no word for “is” in Iklan itu tentang kebun binatang?

Indonesian usually does not use a separate “to be” verb (is/are/am) when linking:

a noun to a noun
a noun to an adjective
a noun to a prepositional phrase like tentang kebun binatang

So:

Iklan itu tentang kebun binatang.
Literally: Advertisement that about zoo.
Meaning: The advertisement is about the zoo.

Other examples:

Dia guru. = He/She is a teacher.
Makanannya enak. = The food is delicious.

The “is” is understood from the structure.

Can I say Iklan itu adalah tentang kebun binatang?

You can hear or see this, but it is generally:

grammatically acceptable
but stylistically awkward / unnecessary in most situations

adalah is mainly used in more formal style to link:

noun = noun
- Dia adalah guru saya. = He/She is my teacher.
or noun = noun phrase
- Tujuan kami adalah kemenangan. = Our goal is victory.

When the predicate begins with a preposition like tentang, Indonesians normally drop adalah:

Iklan itu tentang kebun binatang. ✅ (natural)
Iklan itu adalah tentang kebun binatang. ⚠️ (possible, but sounds heavy/over-formal or translated from English)

So for everyday Indonesian, avoid adalah here.

What exactly is tentang? Is it a verb, preposition, or something else?

tentang is a preposition meaning about / concerning / regarding.

Pattern:

tentang + noun / noun phrase

Examples:

Buku ini tentang sejarah Indonesia. = This book is about Indonesian history.
Kami berbicara tentang rencana liburan. = We talked about vacation plans.

Other words with a similar meaning:

mengenai = about, regarding (a bit more formal)
soal = about, regarding (more informal, often spoken)
perihal = regarding (quite formal, often in letters or official documents)

In your sentence, tentang kebun binatang = about the zoo / about zoos.

Is the word order Iklan itu tentang kebun binatang fixed? Can I move tentang kebun binatang?

In a neutral declarative sentence like this, the standard and natural word order is:

Subject + (demonstrative) + predicate
Iklan itu (subject) tentang kebun binatang (predicate)

You could move tentang kebun binatang to the front for emphasis or a special context:

Tentang kebun binatang, iklan itu.
(Something like: As for the zoo, that advertisement is about it.)

But this kind of fronting:

sounds more literary or rhetorical
usually needs a context where you’re contrasting topics

So for normal speech/writing: keep Iklan itu tentang kebun binatang.

What does kebun binatang literally mean, and is it always translated as “zoo”?

Literally:

kebun = garden, plantation
binatang = animal(s)

So kebun binatang literally is “animal garden”, but in natural English it is simply “zoo”.

In modern Indonesian, kebun binatang is the standard, everyday term for zoo, and it almost always translates that way in normal contexts.

Is kebun binatang singular or plural? How would I say “zoos”?

By default, kebun binatang can be singular or plural, depending on context. Indonesian often does not mark plural explicitly.

So:

Iklan itu tentang kebun binatang.
Can mean:
- The ad is about a zoo / the zoo, or
- The ad is about zoos (in general)

If you really need to make plural explicit, you can say:

kebun-kebun binatang = zoos (reduplication)
banyak kebun binatang = many zoos
beberapa kebun binatang = several zoos

Example:

Film itu tentang beberapa kebun binatang di Asia.
= The film is about several zoos in Asia.

What is the difference between binatang and hewan?

Both can mean “animal”, but there are some tendencies:

binatang
- very common in everyday speech
- can sometimes sound a bit more colloquial
- in some contexts or tones, it can be used as an insult (like “you animal!”)
hewan
- often used in more scientific / educational contexts
- feels slightly more neutral/formal

In kebun binatang, the fixed, idiomatic phrase is with binatang, not hewan.
kebun hewan would sound odd and is not the usual term for zoo.

If I remove itu and just say Iklan tentang kebun binatang, does it still mean “The advertisement is about the zoo”?

Without itu, the structure changes:

Iklan itu tentang kebun binatang.
= full sentence: The advertisement is about the zoo.
Iklan tentang kebun binatang
= more like a noun phrase: an advertisement about the zoo / zoo advertisement

So:

with itu, it’s clearly a statement (subject + predicate).
without itu, it is often interpreted as a phrase (used as a title, label, or part of a longer sentence):
- Saya melihat iklan tentang kebun binatang.
  = I saw an advertisement about the zoo.

If you want a standalone sentence in Indonesian, keep itu (or ini) or use a clear subject.