Just wondering, why would a composer write a piece in 6/8 instead of 6/4 or 3/4? It seems useless to me. I searched around here, and found some quasi-answers, things like "it has an eighth note feel" or whatever, but if eighth notes get the beat in 6/8, then what's the difference? Please excuse my lack of knowledge and such, i tried to get into music theory class but didn't. 
