"They enter the restaurant."
Translation:그들은 식당에 들어가요.
the word for restaurant was not given in Korean so I guessed and I do not know what word is being used here for "restaurant."
식당 is the word for restaurant here. 에 is the location particle.
Konglish 레스토랑 is also used sometimes in Korea.
As well as less common 식점 (food point, literally) for instance.
And others, for sure.
Indeed, there are many words for "dining place" in Korean and they all seem to have slightly different nuances. FYI:
1) 레스토랑 = restaurant
Literally, mean restaurant yet many Koreans usually associate 레스토랑 with some expensive places, often serving western or western-Korean fusion rather than orthodox Korean. For example,
I had a date with her in a restaurant. = 나는 레스토랑에서 그녀와 데이트 했다
2) 음식점, 식당 the very neutral word for eating place - can be upscale or humble, safest word to use as it can be used for all occasions
3) 구내식당 = canteen (in a school or a company)
4) 학생식당 = school canteen
5) 분식집 = 분식점 = snack bar, snack place
분식 means snack in Korean yet you can still have a proper meal in reality. Usually small and humble, good value for money places targeting young rather than old.
6) 가정식 = 집밥 = homemade meal
집= house, home
밥 = cooked rice or meal
저는 집밥을 가장 사랑합니다 = I love the homemade meal most.
우리 같이 밥먹자! = Let us have a meal together (casual form, suggesting for a meal together)
같이 = together
7) name of dish + 집 = > eating place with some clear focus in terms of menu etc.
- 피자집 = a pizza place
- 국수집 - a noodle place
- 도시락집 = a lunchbox place (도시락=lunchbox) http://bit.ly/2DXFWLr
- 햄거버집 = a hamburger place (ex. 버거킹)
- 빵집 = bakery (빵+집)
- 치킨집 = fried chicken place http://bit.ly/2nye2eU
- 중국집 = a Chinese food place (This is the one and only exception as there are no other examples as such. For example Koreans never say 미국집 nor 일본집)
일본 레스토랑 = 일본 음식점 = 일식당 = Japanese restaurant
P.S: I inserted some GOOGLE image search results as it helps one to understand what a word or concept exactly means in the native's head. ;)