oneureun sae banjireul kkigo hakgyoe gasseo.

은 is the topic marker. It sets today up as the topic of the sentence, often with a nuance like as for today or today, ....

So:

• 오늘 갔어 = I went today
• 오늘은 갔어 = As for today, I went / Today, ...

In real speech, 오늘은 can also give a slight contrast, depending on context:

• 오늘은 새 반지를 끼고 학교에 갔어. = Today, I went to school wearing a new ring.
  • This might subtly suggest today was special, or contrast with other days.

You do not always need 은, but it is very natural here.

Both 새 and 새로운 can mean new, but they are used a little differently.

• 새 반지 = the most natural, everyday way to say a new ring
• 새로운 반지 = also possible, but can sound a bit more descriptive, formal, or emphatic depending on context

A very important point: 새 is not just a shortened casual form here. It is a very common determiner-like form used directly before nouns:

• 새 옷 = new clothes
• 새 신발 = new shoes
• 새 반지 = new ring

So in this sentence, 새 반지 is simply the most natural phrasing.

반지 means ring.

The particle 를 is the object marker, showing that ring is the thing affected by the verb 끼다.

So:

• 반지 = ring
• 반지를 = ring + object marker

Because the action is to wear/put on a ring, the ring is the object:

• 반지를 끼다 = to wear a ring / to put on a ring

Here, 끼다 means to put on or to wear something that is fitted onto a body part, especially:

• rings
• gloves
• glasses
• contact lenses

Examples:

• 반지를 끼다 = to wear/put on a ring
• 안경을 끼다 = to wear glasses
• 장갑을 끼다 = to wear gloves

This is different from other Korean wear verbs:

• 입다 = wear clothes
• 쓰다 = wear something on the head
• 신다 = wear shoes
• 차다 = wear a watch, bracelet, or something strapped on
• 메다 = wear/carry something over the shoulder, like a backpack
• 끼다 = wear something inserted/fitted, like a ring or glasses

So 반지를 끼다 is exactly the right verb.

In this sentence, 끼고 is best understood as wearing or having put on.

The ending -고 connects verbs and often means and, but the natural English translation depends on context. Here:

• 반지를 끼고 학교에 갔어 = I wore a ring and went to school = more naturally, I went to school wearing a ring

So grammatically it is put on/wear + and + go, but in English we often express it as wearing.

Usually, yes. The normal interpretation is:

1. they put on the ring
2. they went to school with it on

So the sentence implies that the ring was already on when they went to school.

However, -고 is not always a strong sequence marker like after doing X. It often just links actions. In this kind of sentence, though, the natural understanding is that the person went to school wearing the new ring.

가다 means to go, and destinations are marked with 에.

So:

• 학교에 가다 = to go to school

Here, 에 marks the place you are going to.

By contrast, 를 marks a direct object, and 가다 normally does not take the destination as a direct object in standard Korean.

So:

• 학교에 갔어 = correct
• 학교를 갔어 = not standard for went to school

Because the sentence is talking about something that happened today, but it is still a completed event from the speaker’s point of view.

• 가다 = to go
• 갔어 = went

So the sentence describes a past action:

• Today, I went to school wearing a new ring.

Even if it happened earlier on the same day, Korean still uses the past tense for a completed action.

Yes. 갔어 is the informal, casual ending.

Levels you might compare:

• 갔어 = casual/informal
• 갔어요 = polite
• 갔다 = plain style, often used in writing, narration, or diaries

So this sentence sounds like something you would say to:

• a friend
• someone younger
• someone you are close to

A polite version would be:

• 오늘은 새 반지를 끼고 학교에 갔어요.

Korean often leaves out the subject when it is obvious from context.

So even though English usually needs I, Korean does not have to say it:

• 오늘은 새 반지를 끼고 학교에 갔어. = Today, I went to school wearing a new ring.

The speaker is understood from context. This is extremely common in Korean.

If you did include the subject, it might be:

• 나는 오늘은 새 반지를 끼고 학교에 갔어.

But in many situations that sounds unnecessary unless you want emphasis or contrast.

Yes, that is possible as a more literal interpretation.

Because 끼다 can mean both:

• to put on
• to wear

the sentence can literally be understood as:

• I put on a new ring and went to school.

But in natural English, the smoother translation is usually:

• I went to school wearing a new ring.

That better matches how Korean is linking the actions in context.

Yes. 오늘은 can make the sentence feel a little more like today in particular.

Depending on context, it could suggest things like:

• Today I did something different
• At least today, I wore a new ring
• As for today, this is what happened

For example, maybe:

• the speaker does not usually wear rings
• the ring is newly bought
• today was a special day
• the speaker is contrasting today with yesterday or other days

So 오늘은 is not just a time word; it can also add a subtle topic/contrast feeling.