Der Zug hält an der Station.

Because the two der forms are doing different jobs.

• Der Zug: here der is the masculine nominative singular article, because Zug is masculine and it is the subject of the sentence.
• an der Station: here der is the feminine dative singular article, because Station is feminine and it comes after the preposition an, which uses the dative here.

So the same word der can represent different case/gender combinations. That is very common in German.

Because the subject is Der Zug, which is third-person singular: he/it form.

The verb halten is the infinitive, like to stop or to hold.
When you conjugate it:

• ich halte
• du hältst
• er/sie/es hält
• wir halten
• ihr haltet
• sie/Sie halten

Since der Zug is grammatically er-type singular, you use hält.

Because halten is a strong verb. In the 2nd person singular and 3rd person singular present tense, its stem vowel changes from a to ä.

So:

• ich halte
• du hältst
• er/sie/es hält

This kind of vowel change is something you just have to learn with certain verbs. Other common examples are:

• fahren → du fährst, er fährt
• laufen → du läufst, er läuft

Because an is a two-way preposition. That means it can take:

• dative for a location
• accusative for direction toward something

In this sentence, the station is the place where the train stops, so German treats it as a location:

• an der Station = at the station

If you used an die Station, it would suggest movement toward the station rather than being located there as the stopping point.

Here an means something like at or by.

So an der Station means the train stops at the station.
This is one of those cases where German uses a preposition a bit differently from English, so it is best learned as a natural expression.

Depending on context, German might also use other prepositions with places:

• am Bahnhof = at the train station
• in Berlin = in Berlin
• vor dem Bahnhof = in front of the station

It is understandable, but it depends on context.

For a train station, German very often uses Bahnhof.
For a stop on a route, especially for buses, trams, or subways, Haltestelle is also common.

So depending on what is meant, you might also hear:

• Der Zug hält am Bahnhof.
• Der Zug hält an der Haltestelle.

Station is possible, but it can sound more general. In everyday German, Bahnhof is often the most natural word for a train station.

Yes. halten has several meanings, and to stop is one of them.

Common meanings of halten include:

• to hold: Er hält ein Buch.
• to stop: Der Zug hält am Bahnhof.
• sometimes to keep or to observe, depending on the phrase

This is very normal in German: one verb can cover several related meanings.

They are related, but not identical.

• halten can mean to stop in contexts like trains, buses, or vehicles stopping at a place.

  • Der Zug hält am Bahnhof.

• anhalten often means to come to a stop or to make someone/something stop.

  • Das Auto hält an.
  • Die Polizei hält das Auto an.

• stoppen is also used, but it can sound a bit more direct or modern, and in some contexts a little less idiomatic than halten for trains.

  • Der Zug stoppt is understandable, but Der Zug hält is more natural in many situations.

So in your sentence, hält is a very normal choice.

Because German main clauses normally put the finite verb in second position.

So the pattern is:

• subject
  • finite verb
    • other information

Here:

• Der Zug = subject
• hält = finite verb
• an der Station = prepositional phrase

You could also move another element to the front, but then the verb still stays second:

• An der Station hält der Zug.

That version is grammatical, but it changes the emphasis. The original sentence is the most neutral word order.