Hi Văn Tuấn Kiệt, 잔디 = grass. lawn, turf 풀 = grass 잔디 refers to short grass and usually that is mowed regularly. 풀 refers to grass in general. It includes all kinds of grass regardless of whether it is mowed or not. Ex. - 우리는 공원 잔디 위에 앉아있었다. (We were sitting on grass in park) - 아기 염소는 풀을 먹고 있었다. (The baby goat was eating grass) Hope it helps,