The fez was hat that was worn by people in hot climates, like the desert. It is usually red and has some thread coming out of the top, like in the picture below. It is often worn by the current Doctor in the British TV show called Doctor Who, because of the widely known fact that fez's are cool.

Maroon Fez with Black Tassel

Fez Doctor

The doctor with a fez, as fez's are cool.