This is the 12033rd most frequent Korean word.
놀이터에서
"At the playground."
In this sentence, "놀이터에서" indicates the location where the action of playing (놀고 있어요) is taking place. "에서" is a particle used to denote the location of an activity.
아이들이 놀이터에서 놀고 있어요.
The children are playing at the playground.
Here, "놀이터에서" specifies the location where the accident (사고가 났어요) occurred. "에서" marks the source or venue of the event.
놀이터에서 사고가 났어요.
An accident occurred at the playground.
"놀이터에서" in this sentence refers to the location where the meeting (모임을 가졌어요) was held. Again, "에서" is used to indicate the place of the activity.