Learn Hardcore Korean: jigeum bakkeseo chingureul gidarigo isseoyo.

기다려요 can mean “I wait” (habitual action) or “I will wait.”
기다리고 있어요 specifically means “I am waiting right now.”
If you omit -고 있다, you lose the sense that the action is ongoing at this moment.

In 기다리고 있어요, is 있다 the same verb that means “to exist,” or is it just a helper?

Here 있다 is an auxiliary (helper) verb, not the main “to exist” verb. It combines with -고 to form -고 있다, which expresses continuous or ongoing action.
Contrast:

Auxiliary use (progressive): 기다리고 있어요 = “I am waiting.”
Existential use: 집에 있어요 = “I am at home.” (Here 있다 means “to be located/exist.”)

Why is it 밖에서 instead of 밖에, 바깥에, or 바깥에서?

밖 means “outside.” To mark the location of an action, you attach -에서: 밖에서 = “outside (where something happens).”
밖에 is a completely different particle meaning “only” when used with negatives (e.g., 아무것도 밖에 안 보여요 = “I can only see outside”).
바깥 is just a longer noun form of “outside,” so 바깥에서 is grammatically okay but a bit more formal or descriptive. In everyday speech, 밖에서 is most common.

Why do we say 친구를 with the particle -를, and can we drop it?

기다리다 is a transitive verb that takes a direct object, so you mark the thing you’re waiting for with -을/를: 친구를 기다리다 = “to wait for a friend.”
In casual spoken Korean, people sometimes drop object particles if the meaning is clear:

Full form: 친구를 기다리고 있어요
Casual drop: 친구 기다리고 있어요
Omitting -를 is fine in informal contexts, but including it is clearer and more grammatically complete.

There’s no word for “I” in this sentence; how do we know who is waiting?

Korean commonly omits the subject when it’s clear from context. Here, 지금 밖에서 친구를 기다리고 있어요 naturally implies I (the speaker). If you needed to specify or emphasize the subject, you could add 저(가):

저 지금 밖에서 친구를 기다리고 있어요 = “I am waiting for my friend outside right now.”

Where can we place 지금 in a Korean sentence? Does it always have to be at the front?

Time adverbs like 지금 (“now”) are flexible in Korean. Common positions:
• At the very start for emphasis: 지금 밖에서 친구를 기다리고 있어요.
• After the location: 밖에서 지금 친구를 기다리고 있어요.
• Even before the verb, though less usual: 친구를 기다리고 있어요, 지금 밖에서.
Putting 지금 up front is the clearest way to highlight that the action is happening right now.

What politeness level is 있어요? How formal or casual is this sentence?

The -요 ending on 있어요 makes the sentence polite informal (often called 요-form).

Use this form with strangers, acquaintances, or anyone you need to show basic respect to.
To be more formal, switch to -습니다 form: 기다리고 있습니다.
To be more casual with close friends or younger people, drop 요: 기다리고 있어.

What’s the difference between 밖 and 바깥?

Both mean “outside,” but:
• 밖 is the standard, shorter noun form used in most conversation.
• 바깥 is a slightly longer, more descriptive form.
You’ll almost always hear 밖에서 rather than 바깥에서, but both are grammatically correct.

Can you rearrange 지금, 밖에서, and 친구를 in this sentence? Does the word order matter?

Korean word order is relatively flexible as long as the verb stays at the end. You can shuffle time, place, and object to change emphasis:

Neutral: 지금 밖에서 친구를 기다리고 있어요.
Emphasize location: 밖에서 지금 친구를 기다리고 있어요.
Emphasize object: 친구를 밖에서 지금 기다리고 있어요.
All versions mean essentially the same thing; the default [Time] [Place] [Object] [Verb] is best for learners.