Learn Hardcore Korean: chinguwa hamkke jibeseo chumchwoyo.

와 is a coordinate particle meaning “and” or “with” when attached to a noun ending in a vowel. In 친구와, it means “with a friend.” If the noun ended in a consonant, you would use 과 instead (e.g., 학교와 같이).

Why is 함께 used here, and how is it different from 같이?

Both 함께 and 같이 mean “together.”

함께 is a bit more formal or literary.
같이 is more colloquial and common in everyday speech.
You could say 친구와 같이 집에서 춤춰요, and the meaning stays essentially the same.

What does 집에서 indicate?

집 means “home/house,” and 에서 is a location particle marking where an action takes place. So 집에서 means “at home.” If you wanted to say to home, you’d use 집에.

Why is the verb 춤춰요 used instead of 춤추어요 or 춤추다?

The dictionary form of the verb is 춤추다 (to dance).

In standard polite speech, you drop -다 and attach -어요: 춤추 + 어요 → 춤춰요.
Koreans often contract 추 + 어요 to 춰요 for smoother pronunciation.

Is this sentence present progressive (“are dancing”) or simple present (“dance”)?

Korean doesn’t distinguish between simple present and present progressive in the same way English does. 춤춰요 can mean both “(We) dance” (habitually) and “(We) are dancing” (right now). To emphasize ongoing action, you could add 지금: 친구와 함께 집에서 지금 춤춰요.

Can I change the word order to 집에서 친구와 함께 춤춰요?

Yes. Korean word order is flexible because of particles. 집에서 친구와 함께 춤춰요 still means “We dance at home together with a friend.” However, putting 집에서 first slightly emphasizes the location.

How would I make this sentence more casual or more formal?

Casual/informal: 친구랑 같이 집에서 춤춰. (drop 요, use -어 ending)
More formal: 친구와 함께 집에서 춤춥니다. (use 한다-formal -습니다 ending)

Can I replace 춤춰요 with 춤을 춰요?

Yes. 춤을 추다 literally splits 춤 (dance) and 추다 (to dance). So 춤을 춰요 is perfectly natural and slightly more explicit: 친구와 함께 집에서 춤을 춰요.