it is modal particle. we use 啊 to make a declarative sentence become a exclamatory sentence or a interrogative sentence. if puntuation mark of that sentence is "?" it is a interrogative sentence. for example:是谁啊? if puntuation mark of that sentence is "！" it is a exclamatory sentence. for example:看看花，划划船，多高兴啊! of course,this word -啊- has other meaning,if you look up in the chinese dictionary,you will find there are several pages that used to explain this word

쉽게 말하면 '꽃을 보면서 뱃놀이도 하니까 얼마나 재미있고 기뻐요'라는 듯인데요 잘 이해하세요?