seonsaengnim seolmyeongeul hyudaeponeuro nogeumhae dumyeon najunge bokseuphagi pyeonhaeyo.

In Korean, the possessive marker 의 is often omitted when the relationship is obvious.

So 선생님 설명 literally looks like teacher explanation, but it naturally means the teacher’s explanation.

Both are possible:

• 선생님 설명 = natural, common
• 선생님의 설명 = also correct, a bit more explicit

In everyday speech, Korean often leaves out 의 when it is easy to understand from context.

Because 설명 is the thing being recorded.

The verb is 녹음하다 = to record, and the direct object of that verb is marked with 을/를:

• 설명을 녹음하다 = to record the explanation

So in this sentence:

• 선생님 설명을 = the teacher’s explanation as the object
• 녹음해 두면 = if you record it and keep it / have it recorded for later

Here, 으로 marks the tool or means used to do something.

So:

• 휴대폰으로 = with a cellphone / using a cellphone

Examples:

• 펜으로 써요. = I write with a pen.
• 컴퓨터로 공부해요. = I study using a computer.
• 휴대폰으로 녹음해요. = I record it with my phone.

So it does not mean to the phone here. It means by means of a phone.

This is an important nuance.

• 녹음하면 = if you record it
• 녹음해 두면 = if you record it and leave it prepared for later use

The pattern -아/어 두다 means doing something in advance, for future convenience, or and leaving it that way.

So:

• 문을 열어 두다 = to leave the door open
• 미리 적어 두다 = to write it down in advance
• 녹음해 두다 = to record it in advance so you can use it later

In this sentence, 녹음해 두면 strongly matches the idea of reviewing later.

-면 means if or sometimes when, depending on context.

Here:

• 녹음해 두면 = if you record it and keep it for later
• 나중에 복습하기 편해요 = it’s convenient to review later

So the whole structure is:

• X-면 Y = If X, Y

It is a very common conditional pattern in Korean.

나중에 means later, and it tells you when the reviewing happens.

Korean adverbs like 나중에 are often placed before the verb phrase they modify.

So:

• 나중에 복습하다 = to review later
• 나중에 복습하기 편하다 = it is convenient to review later

The word order is very natural in Korean:

• time expression first
• then the action

Literally, it is:

• 복습하다 = to review
• 복습하기 = reviewing / to review
• 편하다 = to be comfortable, easy, convenient
• 편해요 = polite present form of 편하다

So 복습하기 편해요 means:

• it’s easy to review
• it’s convenient for reviewing
• it makes reviewing easier

The -기 turns the verb into something like a noun or activity:

• 읽기 = reading
• 쓰기 = writing
• 복습하기 = reviewing

So 복습하기 편해요 is literally something like reviewing is convenient/easy.

Both can relate to convenience, but 편하다 is more common and natural in many everyday situations like this.

• 편하다 = comfortable, easy, convenient
• 편리하다 = convenient in a slightly more formal or functional sense

In this sentence, 복습하기 편해요 sounds very natural because it means it’s easy/convenient to review.

If you said 복습하기 편리해요, it would sound more formal or less conversational.

The object is understood from context.

The sentence talks about recording the teacher’s explanation, so when it says 복습하다 later, it naturally means:

• review that explanation
• review the lesson/content you recorded

Korean often omits objects when they are obvious.

English usually prefers to repeat them more often, but Korean does not need to if the listener already knows what is meant.

편해요 is the polite informal style, also called the -아요/어요 style.

It is very common in everyday speech and neutral conversation.

Compare:

• 편해요 = polite, natural, conversational
• 편합니다 = more formal
• 편해 = casual, plain-to-friend style

So the sentence is polite and natural, but not stiff.

It is made from two parts:

• 녹음하다 = to record
• 두다 = to put / leave

In the grammar pattern -아/어 두다, the second verb 두다 loses its original literal meaning and becomes a grammatical helper meaning:

• do something in advance
• leave something done
• keep something ready

So 녹음해 두다 is best understood as one unit of meaning:

• to record and keep it for later use

녹음 is pronounced approximately like 노금.

That is because final consonant pronunciation changes in Korean make 녹음 sound more like:

• 녹음 → [노금]

A few useful pronunciations from the sentence:

• 선생님 → roughly seon-saeng-nim
• 설명 → roughly 설명, with the final ㅁ clearly pronounced
• 휴대폰 → roughly hyu-dae-pon
• 복습 → often sounds close to 복씁
• 녹음 → 노금

It is very normal if the spelling and pronunciation do not match perfectly at first; Korean has several regular sound-change rules like this.

Yes. In everyday Korean, both are used.

• 휴대폰 = cellphone, mobile phone
• 핸드폰 = cellphone, very common in speech

So these both work:

• 휴대폰으로 녹음해 두면...
• 핸드폰으로 녹음해 두면...

휴대폰 may sound a little more standard, while 핸드폰 is very common in casual conversation.