Wish Size Medium Green Patterned Shrug

I gotta admit, I'm having a Country Comes to Town time with this top. Can someone tell me what the button is for? I feel like I'm doing something wrong, but it looks so cute the way I have it on my friend, Torsola. If it's on correctly and the button is just there for some superstition of the designer, I'll carry on with my description. Very sheer material in the prettiest colors ever, and I love the way it hangs unevenly! Yes, I put it on, and it's so light and airy, felt like I was putting out a happy vibe. :) I would put some tiny, plain, entirely insignificant cami or tank or bra underneath, plain black leggings, and let this top take center stage. (I really do love the colors, not having to cross my fingers or anything while writing.)