gwangaegi gongyeonjang apeseo gamanhi gidaryeosseo.

이 is the subject marker. It shows that 관객 is the subject of the sentence.

• 관객이 = the audience member / spectator(s) as the subject
• It answers the idea of who waited?

A learner may also wonder why it is not 관객은. Both are possible, but the nuance changes:

• 관객이 공연장 앞에서 가만히 기다렸어.
  More like: It was the spectator(s) who waited...
• 관객은 공연장 앞에서 가만히 기다렸어.
  More like: As for the spectator(s), they waited...

So 이/가 often sounds more neutral for introducing the subject or focusing on who did the action.

This part breaks down like this:

• 공연장 = performance hall / theater / venue
• 앞 = front
• 에서 = at / in / from, marking the place where an action happens

So:

• 공연장 앞에서 = in front of the performance hall

The important point is 에서. It is used because waiting is an action happening at that location.

Compare:

• 공연장 앞에 = in front of the hall (location/existence)
• 공연장 앞에서 = at/in front of the hall, doing some action there

Since 기다리다 is an action verb, 에서 is the natural choice.

Because the sentence describes an action happening there.

A very useful beginner rule is:

• 에 often marks a place of existence or destination
• 에서 often marks a place where an action takes place

Here, the person is waiting, so Korean uses 에서:

• 공연장 앞에서 기다렸어 = waited in front of the theater

If you said 공연장 앞에 있었어, that would mean was in front of the theater, focusing on being there, not the action of waiting.

가만히 is an adverb. In this sentence, it means something like:

• still
• quietly
• without moving around
• calmly

So it describes how the waiting happened.

It gives the feeling that the spectator(s) waited:

• without fidgeting
• without making noise
• without doing much else

In other contexts, 가만히 can also mean things like:

• stay still
• leave it alone
• be quiet / don’t move

So its exact nuance depends on context, but here it modifies 기다렸어.

기다렸어 comes from the dictionary form 기다리다 (to wait).

Formation:

• 기다리다 → stem 기다리-
• past tense -었-
• casual ending -어

So:

• 기다리 + 었어 → 기다렸어

This means waited in a casual, plain speech style.

Related forms:

• 기다리다 = to wait
• 기다려 = wait / am waiting (casual, depending on context)
• 기다렸어 = waited
• 기다렸어요 = waited (polite)
• 기다렸습니다 = waited (formal)

Because Korean is typically a subject–object–verb language, and the verb normally comes at the end of the clause.

So in this sentence:

• 관객이 = subject
• 공연장 앞에서 = place
• 가만히 = adverb
• 기다렸어 = verb

English usually puts the verb earlier:

• The spectator waited quietly in front of the theater.

Korean naturally saves the main action until the end:

• 관객이 공연장 앞에서 가만히 기다렸어.

This verb-final pattern is one of the biggest differences from English.

Yes, adverbs in Korean are often fairly flexible.

For example, these can all sound natural depending on emphasis:

• 관객이 공연장 앞에서 가만히 기다렸어.
• 관객이 가만히 공연장 앞에서 기다렸어.
• 가만히 관객이 공연장 앞에서 기다렸어. (less neutral in everyday use, but possible in the right context)

The most neutral version here is probably the original sentence, where 가만히 comes right before the verb it modifies.

Putting an adverb closer to the verb is very common in Korean.

It can be either singular or plural, depending on context.

Korean often does not mark plural unless it needs to. So:

• 관객이 could mean the spectator
• or the spectators / audience members

If the speaker wants to make plurality explicit, they can say:

• 관객들이 = the spectators / audience members

But Korean often leaves that unstated when context already makes it clear.

This is very normal, and it is one reason Korean sentences can sound less specific than English about number.

Good question. In Korean, 기다리다 often takes a direct object when the thing or person being waited for is stated:

• 친구를 기다렸어. = I waited for my friend.

But the object can be omitted if it is:

• obvious from context
• unimportant
• intentionally left unstated

So in this sentence, the focus is on the fact that the spectator(s) waited quietly in front of the venue, not on exactly whom or what they were waiting for.

That omission is very natural in Korean.

기다렸어 is in the casual/informal speech style.

It would be used with:

• close friends
• younger people
• family
• someone you speak casually with

More polite versions would be:

• 관객이 공연장 앞에서 가만히 기다렸어요. = polite
• 관객이 공연장 앞에서 가만히 기다렸습니다. = formal

So the sentence is not rude by itself, but it is definitely not formal. The speaker is using a relaxed style.

Yes, it could:

• 관객은 공연장 앞에서 가만히 기다렸어.

But the nuance changes.

Very roughly:

• 이/가 highlights the subject itself, or presents it more directly
• 은/는 marks the topic and can add contrast or background information

So:

• 관객이... feels like the spectator(s) did this
• 관객은... feels more like as for the spectator(s), they...

If this sentence is simply describing what happened, 이/가 is very natural.
If the speaker is contrasting the audience with someone else, 은/는 might be better:

• 배우는 들어갔고, 관객은 공연장 앞에서 가만히 기다렸어.
  The actors went in, and the audience waited quietly in front of the venue.