Das Schwein schläft im Stall.

Because Schwein is a neuter noun in German, so its basic article is das.

• der = masculine
• die = feminine
• das = neuter

So the dictionary form is das Schwein.

This grammatical gender does not mean the pig is biologically male. It is just a grammar category. If you specifically wanted to say boar or sow, German has other words for that.

In this sentence, das is the definite article, meaning the.

So:

• das Schwein = the pig

German articles change depending on gender, case, and number, so the is not always just one word in German.

Because all nouns are capitalized in German.

So in this sentence:

• Schwein is a noun, so it gets a capital letter
• Stall is also a noun, so it gets a capital letter
• schläft is a verb, so it stays lowercase

This is one of the most noticeable spelling differences between English and German.

Because the verb has to be conjugated to match the subject.

The infinitive is schlafen = to sleep.

With das Schwein = it / the pig, you need 3rd person singular:

• ich schlafe
• du schläfst
• er/sie/es schläft

Since das Schwein is singular, the correct form is schläft.

Some strong verbs in German change their stem vowel in the 2nd person singular and 3rd person singular present tense.

So schlafen becomes:

• du schläfst
• er/sie/es schläft

This a → ä change is just part of how this verb works, and it has to be memorized as part of the conjugation.

im is a contraction of in dem.

So:

• im = in dem

The noun Stall is masculine: der Stall.

After in, when it answers the question where?, German uses the dative case.
So:

• der Stall → dem Stall
• in dem Stall → im Stall

That is why im Stall is correct.

Because here in describes location, not direction.

A helpful rule:

• Where? → usually dative
• Where to? / into where? → usually accusative

In this sentence, the pig is already in the barn and sleeping there, so it is location:

• Das Schwein schläft im Stall. = where is it sleeping? In the barn.

Compare:

• Das Schwein geht in den Stall. = The pig goes into the barn.
  Here there is movement toward a destination, so accusative is used.

This is the normal German word order for a basic main clause:

subject + verb + other information

So:

• Das Schwein = subject
• schläft = verb
• im Stall = location

German has a very important rule: in a normal main clause, the conjugated verb usually comes in second position.

That is true here:

1. Das Schwein
2. schläft

Yes. That is also correct.

German often allows you to move parts of the sentence for emphasis, as long as the conjugated verb stays in second position.

So both are correct:

• Das Schwein schläft im Stall.
• Im Stall schläft das Schwein.

The second version emphasizes where the pig is sleeping.

A rough pronunciation guide:

• sch sounds like sh
• lä has an ä sound somewhat like the vowel in bed, though not exactly the same
• ft is pronounced clearly at the end

So schläft sounds roughly like shleft.

Also:

• Schwein starts with schw, where sch = sh
• the ei in Schwein sounds like English eye

So Schwein is roughly shvine.

Stall usually means a place where farm animals are kept, such as a barn, sty, pen, or stable, depending on context.

In this sentence, with Schwein, a natural English translation might be:

• The pig is sleeping in the barn.
• or The pig is sleeping in the sty.

The exact English word can vary, but the German grammar stays the same.

The plural of das Schwein is die Schweine.

So the sentence becomes:

• Die Schweine schlafen im Stall. = The pigs are sleeping in the barn.

Notice the changes:

• das Schwein → die Schweine
• schläft → schlafen

The location part im Stall stays the same here.

Yes, das can mean different things in German depending on context.

It can be:

• a definite article: das Schwein = the pig
• a demonstrative or pronoun in other situations: Das ist gut. = That is good.

In Das Schwein schläft im Stall, it is clearly the article belonging to Schwein, so here it means the, not that.