Спустя час поезд приехал.

Here спустя means after or an hour later.

In Спустя час поезд приехал, it introduces the amount of time that passed before the event happened. So the structure is:

спустя + amount of time = after ... / ... later

Common examples:

• спустя минуту = a minute later
• спустя год = a year later
• спустя долгое время = after a long time

It is often used in narration and can sound a little more literary or formal than some other options.

Because спустя normally takes the accusative case, and час is the accusative singular form here.

For masculine inanimate nouns like час, the accusative singular looks the same as the nominative singular:

• nominative: час
• accusative: час

So:

• спустя час = after an hour

Compare:

• спустя минуту = after a minute
  Here you can see the accusative more clearly, because минута becomes минуту.

They are very close, and in many contexts both can be translated as in an hour / after an hour.

But there is often a nuance:

• через час usually means in an hour, measured from now or from some reference point
• спустя час emphasizes that an hour passed, and then the event happened

So in a story:

• Через час поезд приехал = The train arrived an hour later / in an hour
• Спустя час поезд приехал = After an hour had passed, the train arrived

Спустя can sound a bit more narrative or descriptive.

Because приехал is perfective past, showing a completed arrival.

• приехать = to arrive (by transport), to come by vehicle, completed action
• приезжать = to arrive / come by transport repeatedly, habitually, or as an ongoing/general action

In this sentence, the train reached its destination at a specific moment, so Russian uses the perfective:

• поезд приехал = the train arrived

If you said приезжал, it would suggest a different meaning, such as repeated visits or a less event-focused statement.

That is the standard marker of the past tense in Russian.

Past tense forms agree in gender and number:

• masculine: приехал
• feminine: приехала
• neuter: приехало
• plural: приехали

Since поезд is a masculine singular noun, the verb is:

• поезд приехал

Поезд is in the nominative case, because it is the subject of the sentence.

It is the thing doing the action of arriving:

• поезд = the train
• приехал = arrived

So the basic structure is:

• [subject in nominative] + [verb]

Because Russian has no articles like a and the.

So поезд can mean:

• a train
• the train

Which one is meant depends on context. In this sentence, English naturally uses the train arrived, but Russian simply says поезд приехал.

Yes. Russian word order is more flexible than English word order.

The sentence:

• Спустя час поезд приехал

could also be:

• Поезд приехал спустя час

Both are grammatical. The difference is mainly in emphasis:

• Спустя час поезд приехал puts the time frame first, which is natural in storytelling
• Поезд приехал спустя час starts with the subject and feels a bit more neutral

Russian word order often changes to highlight what is most important or what connects best with the previous context.

Yes, exactly. Приехать is used for arriving by transport or by vehicle.

That makes it a very natural verb for:

• trains
• cars
• buses
• bicycles
• people arriving by some means of transport

For a train, поезд приехал is completely normal Russian.

Compare:

• поезд приехал = the train arrived
• самолёт прилетел = the plane arrived / flew in
• корабль приплыл = the ship arrived / sailed in

Russian often chooses verbs that reflect the manner of movement more specifically than English does.

Not necessarily from now. It means after an hour had passed from the relevant reference point.

That reference point comes from context. For example:

• We started waiting. Спустя час поезд приехал.
  = We started waiting. An hour later, the train arrived.

So спустя час is relative to whatever moment the story is already talking about.

Yes, it is natural and correct.

It sounds like a simple narrative sentence: first some time passes, then the train arrives.

Depending on context, Russians might also say:

• Через час поезд приехал
• Поезд приехал через час
• Через час поезд прибыл

But Спустя час поезд приехал is perfectly normal, especially in storytelling or written narration.