에 has more meaning than 에서. Both can be used for location, and 에서 gives more stress where “that action” occurred. But I don’t think this is too difficult for non-native speaker. Other difference is 에서 as a meaning of departing place like 학교에서 집까지 걸었다, , we shouldn’t use 에, here. And if you are heading to somewhere, you should use 에, like 도서관에 가다. , and this time you can’t use 에서 here. And 에서 is not for time. You only use 에. And we have several other usage for –에,  Show why someone feel or act like that. 총소리에 놀라다 Show standard why someone think or evaluate like that 예의에 벗어나다 As a conjunction, enumerate things 과일에 음료수에 잔뜩 먹었다

에 is used when u indicate the place/location of someone/something. 에서 is used when you are saying one is at certain place + doing sthg. For example: I am in the bathroom. 저는 목욕실에 있어요. I am in the bathroom having a shower. 저는 목욕실에서 샤워 하고있어요.