A fascinator is a formal headpiece, a style of millinery.

It is formal headwear worn as an alternative to the hat. Usually a large decorative design is attached to a band or clip.

It is a hat and is purely ornamental and it covers very little of the head and offers little or no protection from the weather.

It is sometimes called a hatinator.

Taken from Wikipedia https://en.wikipedia.org/wiki/Fascinator