예약하다([ye-yak-ha-da/reserve]) means book, make booking, hold seat. In polite speech, say 예약해요([ye-yak-hae-yo]).
예약했어요([ye-yak-hae-sseo-yo/reserved]) is the polite past form. Example: 어제 식당을 예약했어요 (I reserved a restaurant yesterday).
예약해야 해요([ye-yak-hae-ya hae-yo/have to reserve]) means must book. Example: 미리 예약해야 해요 (I have to reserve in advance).
예약하다([ye-yak-ha-da/reserve]) means "to reserve". It is used when you book, make booking.
1. Daily: “어디 예약해요? (eo-di ye-yak-hae-yo)”
2. Past: 예약했어요([ye-yak-hae-sseo-yo/reserved]) reserved.
3. Duty: 예약해야 해요([ye-yak-hae-ya hae-yo/have to reserve]) have to reserve.
4. Warning: 예약하지 마세요([ye-yak-ha-ji ma-se-yo/don't reserve]) don't reserve.
A: Where do you reserve?
B: 식당을 예약해요. B: sik-dang-eul ye-yak-hae-yo.B: I reserve a restaurant.
A: 식당을 예약해요? A: sik-dang-eul ye-yak-hae-yo?A: You reserve a restaurant?
B: 네, 식당을 예약해요. B: ne, sik-dang-eul ye-yak-hae-yo.B: Yes, a restaurant. - 예약하다([ye-yak-ha-da/reserve])
A: Did you reserve?
B: 네, 예약했어요. B: ne, ye-yak-hae-sseo-yo.B: Yes, I reserved.
A: 뭐 예약했어요? A: mwo ye-yak-hae-sseo-yo?A: What did you reserve?
B: 호텔을 예약했어요. B: ho-tel-eul ye-yak-hae-sseo-yo.B: I reserved a hotel. - 예약했어요([ye-yak-hae-sseo-yo/reserved])
A: When do you have to reserve?
B: 오늘 예약해야 해요. B: o-neul ye-yak-hae-ya hae-yo.B: I have to reserve today.
A: 오늘 예약해야 해요? A: o-neul ye-yak-hae-ya hae-yo?A: Today?
B: 네, 오늘 예약해야 해요. B: ne, o-neul ye-yak-hae-ya hae-yo.B: Yes, today. - 예약해야 해요([ye-yak-hae-ya hae-yo/have to reserve])
• 예약하다([ye-yak-ha-da/reserve]) reserve / book
- 예약했어요([ye-yak-hae-sseo-yo/reserved]) reserved
- 예약하고 싶어요([ye-yak-ha-go si-peo-yo/want to reserve]) want to reserve
- 예약해야 해요([ye-yak-hae-ya hae-yo/have to reserve]) have to reserve
- 예약하지 마세요([ye-yak-ha-ji ma-se-yo/don't reserve]) don't reserve