inteoneseseo bon gwanggoga saenggakboda jaemiisseosseoyo.

It literally means something like the advertisement seen on the internet.

Korean puts a modifying clause before the noun it describes. So:

• 인터넷에서 = on the internet / from the internet
• 본 = saw / seen
• 광고 = advertisement

So instead of saying the ad that I saw on the internet, Korean says on-the-internet saw ad.

Here, 본 is the noun-modifying form of 보다 (to see).

Because 에서 usually marks the place where an action happens.

In this sentence, the action is seeing the ad, so Korean treats the internet as the place/source where you saw it:

• 인터넷에서 본 광고 = the ad seen on the internet

Using 에 here would sound unnatural, because 에 is more often used for location/existence/direction, while 에서 is commonly used for actions.

A useful comparison:

• 학교에 있어요 = It is at school.
• 학교에서 공부해요 = I study at school.

Likewise:

• 인터넷에서 봤어요 = I saw it on the internet.

본 comes from the verb 보다 (to see).

When Korean verbs modify a noun, they change form. For 보다, the past/adnominal form is 본.

So:

• 보다 = to see
• 본 광고 = the ad (that someone) saw

This is very common in Korean:

• 먹다 → 먹은 음식 = the food that was eaten / the food someone ate
• 가다 → 간 사람 = the person who went
• 보다 → 본 영화 = the movie (someone) saw

So 본 광고 is simply the ad that I/someone saw.

Yes.

Korean often leaves out subjects like I, you, or we when they are understood from context. So 인터넷에서 본 광고 naturally means:

• the ad I saw on the internet
• or more generally the ad seen on the internet

In everyday speech, Korean does not need to say I unless it is important for emphasis or contrast.

생각보다 means than I thought or than expected.

It is made of:

• 생각 = thought
• 보다 = than

This 보다 is not the verb to see here. It is a comparison particle meaning than.

So:

• 생각보다 재미있었어요 = It was more interesting/fun than I thought.
• literally: Compared to my thought, it was interesting.

This expression is very common in Korean and often works like more ... than expected in English.

Examples:

• 생각보다 어려워요. = It’s harder than I thought.
• 생각보다 괜찮아요. = It’s better than I expected.
• 생각보다 커요. = It’s bigger than I thought.

Because 광고 is the subject of the main descriptive part 재미있었어요.

The sentence structure is basically:

• 인터넷에서 본 광고가 = the ad I saw on the internet
• 생각보다 재미있었어요 = was more interesting than I thought

So the ad is the thing being described as interesting, which makes it the subject.

That is why 가 is used.

If you used 를, it would make 광고 the object of a verb, but here the sentence is not saying someone did something to the ad. It is saying the ad was interesting.

재미있었어요 comes from 재미있다, which means to be interesting / fun / entertaining.

Breakdown:

• 재미있다 = to be interesting/fun
• 재미있었어요 = was interesting/fun

This is the past tense polite form.

So the sentence is talking about a past reaction:

• The ad was more interesting than I thought.

A small note: 재미있다 is often translated as to be fun, but depending on context it can also mean interesting, entertaining, or amusing.

It can mean several related things:

• interesting
• fun
• entertaining
• sometimes funny/amusing

For an advertisement, 재미있었어요 usually means it was more entertaining or interesting than expected, not necessarily that it was laugh-out-loud funny.

So in this sentence, interesting or entertaining is often the safest translation.

Yes, very naturally.

생각보다 already implies than I thought / than expected, so Korean does not need to spell out the full comparison every time.

For example:

• 생각보다 맛있어요. = It’s tastier than I thought.
• 생각보다 비싸요. = It’s more expensive than I expected.
• 생각보다 재미있었어요. = It was more interesting than I thought.

This is one of those very common Korean shortcuts that sounds completely natural.

Yes, you could.

Both are possible, but they feel slightly different:

• 인터넷에서 본 광고 = the ad I saw on the internet
• 인터넷에서 봤던 광고 = the ad I had seen on the internet / that ad I remember seeing on the internet

봤던 often adds a slightly more reflective or remembered feeling, as if you are referring back to a particular ad already in your mind.

So:

• 본 = simpler, more neutral
• 봤던 = a bit more like that ad I remember seeing

In many everyday situations, 본 광고 is the more straightforward choice.