Mereka menjaga tempat suci itu.

Because mereka is the subject of the sentence: they.

Indonesian usually follows Subject + Verb + Object, just like English in a basic sentence. So:

• Mereka = they
• menjaga = guard / protect / look after
• tempat suci itu = that sacred place

So the structure is very straightforward.

Yes, mereka means they or them depending on the sentence.

A few useful things to know:

• It does not show gender, so it can refer to men, women, or a mixed group.
• It is normally used for people, not usually for things or animals.
• Indonesian does not change the form the way English does with they/them/their. Context tells you the role.

In this sentence, mereka is the subject, so it means they.

Jaga is the base form, and menjaga is the active verb form with the prefix meN-.

This is very common in Indonesian. The meN- prefix often marks an active verb, especially when the verb has a direct object.

Here:

• jaga = guard, watch, keep watch
• menjaga = to guard / to protect / to look after

Because the sentence has a direct object, tempat suci itu, menjaga is the natural form.

Menjaga can mean several related things, depending on context:

• to guard
• to protect
• to watch over
• to take care of

In this sentence, it most likely means something like:

• They guard that sacred place
• They protect that sacred place
• They look after that sacred place

The exact best translation depends on the situation.

Indonesian verbs do not change form for tense the way English verbs do.

So menjaga can mean:

• guard
• are guarding
• guarded
• will guard

The time is usually understood from:

• context
• time words such as kemarin (yesterday), sekarang (now), besok (tomorrow)
• aspect markers like sedang, sudah, akan

Without any time marker, this sentence is neutral and could be understood as a general present or present situation, depending on context.

Because in Indonesian, adjectives usually come after the noun.

So:

• tempat = place
• suci = holy / sacred
• tempat suci = holy place / sacred place

This is a very common pattern in Indonesian:

• rumah besar = big house
• buku baru = new book
• kota kecil = small city

So tempat suci is the normal word order.

Here, itu means that.

In Indonesian, demonstratives like ini and itu usually come after the noun phrase, not before it.

So:

• tempat suci ini = this sacred place
• tempat suci itu = that sacred place

This is different from English, where this and that come before the noun.

So the word order is normal Indonesian:

• noun + adjective + demonstrative

Because Indonesian does not have articles like a, an, and the.

Whether something is definite or indefinite is usually understood from context.

So tempat suci itu means that sacred place, and the idea of definiteness is already clear because of itu.

If the sentence were just tempat suci, it could mean:

• a sacred place
• the sacred place
• sacred place

depending on context.

Tempat suci literally means sacred place or holy place.

It is a fairly general expression. It does not automatically mean one specific type of building such as:

• masjid = mosque
• gereja = church
• pura = Hindu temple
• kuil = temple

So tempat suci can refer to any place considered sacred in a religious or spiritual sense.

Yes. Itu can do a few different jobs in Indonesian.

Most commonly, it means that, as in this sentence.

But in other contexts, it can also:

• refer back to something already mentioned
• add emphasis
• help identify something already known in the conversation

Still, in tempat suci itu, the simplest and best understanding is that sacred place.

Yes, sometimes Indonesian can omit the subject if it is already clear from context.

For example, if everyone already knows who is being discussed, someone might simply say:

• Menjaga tempat suci itu.

But as a full standalone sentence, Mereka menjaga tempat suci itu is clearer and more complete.

It is normal, neutral Indonesian.

It is:

• grammatical
• natural
• neither especially slangy nor especially stiff

You could hear or read this kind of sentence in:

• conversation
• news
• school materials
• stories

So it is a good standard example of basic Indonesian sentence structure.