Men's shirts have the buttons on the right, but women's blouses have the
buttons on the left.

This is more than just a way to tell whether a
shirt is for men or women.

There is a historical reason for it.

During the Victorian period, buttons were quite expensive, and were
mostly worn by rich people.

Since proper, well-to-do ladies were dressed
by their servants, and most people are right-handed, their buttons were
placed on the servant's right, which is the wearer's left side.

However,
most gentlemen dressed themselves, so their buttons were placed on the
wearer's right side.

Those who could not afford servants copied the style of the wealthy, and
women's buttons thereafter remained on the left.