هم في الشقة.

In Arabic, the present-tense verb to be is usually omitted in simple statements.

So هم في الشقة is literally something like they in the apartment, but it naturally means they are in the apartment.

This is very normal in Modern Standard Arabic.

هم means they.

More specifically, it is the 3rd person masculine plural pronoun. It is used for:

• a group of males, or
• a mixed group of males and females

If the group were all female, Arabic would normally use هنّ instead.

في means in.

It is a preposition, so the word after it is its object, just like English in the apartment.

In Arabic grammar, nouns after prepositions are in the genitive case.

The word begins with the definite article الـ, which usually means the.

But the letter ش is a sun letter, so the l sound of ال assimilates to the next consonant.

So:

• written: الشقة
• pronounced: ash-shaqqa

The sh sound is doubled in pronunciation.

The basic noun is شقة, meaning apartment.

Adding الـ makes it definite:

• شقة = an apartment / apartment
• الشقة = the apartment

So in this sentence, الشقة is simply the apartment.

The final ة is called tāʾ marbūṭa.

In many cases, especially when pausing, it sounds like -a or -ah, so شقة sounds like shaqqa.

In fully inflected formal pronunciation, it can show case endings, so after في it would be الشقةِ, pronounced approximately ash-shaqqati.

But in normal reading and speech, learners will often just hear ash-shaqqa.

A fully vowelled version is:

هُمْ فِي الشَّقَّةِ

This shows:

• هُمْ = hum
• فِي = fī
• الشَّقَّةِ = ash-shaqqati in full grammatical pronunciation

At the end of a sentence, many speakers pause and do not pronounce the final case vowel, so you will often hear ash-shaqqa.

هم في الشقة is a normal and straightforward order.

It starts with هم as the topic or subject, followed by في الشقة as the rest of the statement.

Arabic can sometimes change word order for emphasis. For example, في الشقة هم could be used in a more marked or emphatic way, but it is not the most basic learner form.

So for a beginner, هم في الشقة is the best standard pattern to remember.