jihacheoreseo ieoponeuro eumageul deureoyo.

Because -에서 marks the place where an action happens. In this sentence, the action is listening to music, and that action happens on/in the subway.

• 지하철에서 = in/on the subway as the location of the action
• 지하철에 usually means to the subway / at the subway and is more about destination, location, or existence rather than where an action is actively taking place

So for an action like studying, eating, listening, talking, -에서 is the normal choice for the place where it happens.

-으로 often marks the means, tool, or method used to do something.

So:

• 이어폰으로 = with earphones / using earphones

In this sentence, it tells you how the person is listening to the music.

Other similar examples:

• 버스로 가요 = I go by bus
• 한국어로 말해요 = I speak in Korean
• 젓가락으로 먹어요 = I eat with chopsticks

Here, 이어폰으로 is the instrument or means.

을/를 is the object particle. It marks what the verb is acting on.

• 음악을 들어요 = listen to music

The verb 듣다 takes a direct object in Korean, so the thing being listened to gets 을/를.

You will often hear Koreans drop 을/를 in casual speech if the meaning is obvious:

• 음악 들어요

That is still very common and natural in conversation. But in a textbook-style sentence, keeping 을 is clearer and more standard.

Yes. The dictionary form is 듣다, and 들어요 is its present polite form.

This verb is irregular:

• 듣다
  • -어요
• the ㄷ changes to ㄹ before a vowel
• so it becomes 들어요, not 듣어요

This is called a ㄷ irregular pattern.

A few similar verbs:

• 걷다 → 걸어요 = walk
• 묻다 → 물어요 = ask

So:

• dictionary form: 듣다
• polite present: 들어요

Korean normally puts the verb at the end. A very common basic pattern is:

place + method + object + verb

So in this sentence:

• 지하철에서 = on the subway
• 이어폰으로 = with earphones
• 음악을 = music
• 들어요 = listen

English and Korean organize sentences differently. In English, the verb usually comes earlier. In Korean, the verb is usually saved for the end.

That said, Korean word order is somewhat flexible because particles show each word’s role. But the verb still usually stays at the end.

The subject is omitted because Korean often leaves out information that is already understood from context.

So this sentence could imply:

• 저는 지하철에서 이어폰으로 음악을 들어요 = I listen to music with earphones on the subway
• or 제가 ...
• or even 그는/그녀는 ... depending on context

In everyday Korean, leaving out the subject is extremely common when it is obvious.

들어요 is in the polite casual style, often called 해요체.

It is:

• polite enough for most everyday situations
• very common in conversation
• less formal than 듣습니다
• more polite than plain casual 들어

So the levels would be roughly:

• 들어 = casual, intimate
• 들어요 = polite everyday speech
• 듣습니다 = formal polite

Yes. 지하철 안에서 is also natural.

The difference is:

• 지하철에서 = on/in the subway
• 지하철 안에서 = inside the subway

Adding 안 makes the idea of inside more explicit. Without 안, the sentence is still completely natural and normal.

In careful spelling, it is:

지하철에서 이어폰으로 음악을 들어요

But in natural pronunciation, some sounds change smoothly between syllables. It sounds closer to:

지하처레서 이어포느로 으마글 드러요

A few helpful points:

• 철에서 sounds like 처레서
• 폰으로 sounds like 포느로
• 음악을 sounds like 으마글
• 들어요 sounds like 드러요

These are normal sound changes in spoken Korean, so the written form and spoken form are not always identical.

Yes, to some extent. Because Korean uses particles, you can move parts around for emphasis, as long as the sentence still sounds natural.

For example:

• 이어폰으로 지하철에서 음악을 들어요
• 음악을 지하철에서 이어폰으로 들어요

These are understandable, but the original order is very natural and neutral:

• 지하철에서 이어폰으로 음악을 들어요

So while Korean word order is more flexible than English, some orders feel more basic and common than others.