Fashion is a huge term in the modern world. It is style, comfort, trend, all at the same time! Everybody wants to look fashionable these days. But the problem is that fashion varies with age, geographical boundaries, race, and culture. What is fashionable to one may be out of the world for another. There is no exact definition to good fashion sense.
Geographical location and the culture of an area have a huge role to play in defining the fashion trends of that particular area. A rural Indian woman may consider embroidered saris fashionable while an urban American woman may give that honor to a designer evening gown. The definition of good fashion sense also varies with the geographical locations and culture. You have some sense for fashion, if you are not dressed weirdly.
If you wear an evening gown to a funeral, that would be a fashion nonsense! One is supposed to wear bright colours at marriages in some cultures,....