This is the 6467th most frequent Korean word.
에선
"In" or "at" (used to indicate location or context in a comparison or situation).
'에선' is used here to mark '학교' (school) as the location where the study activity mentioned takes place. This illustrates its functional role as a locational marker.
학교에선 친구들과 함께 공부를 해요.
At school, I study together with friends.
'에선' is applied to '음식점' (restaurant) in this sentence to denote it as the place where the action of experiencing food occurs, again showing its location-indicating property.
음식점에선 다양한 한국 음식을 맛볼 수 있어요.
At restaurants, you can experience various Korean dishes.
'에선' is used with '온라인 환경' (online environment) to signify it as the setting within which the described capability to communicate exists.