The piece of cloth arabs wear on top of their heads is called a shmagh. A shmagh is only called a shmagh if it have the red and white pattern on it. It looks like the one Yassir Arafat wears except his is black and white. A ghotrah on the other hand, is purely white.
The black rounded circle worn on top is used to hold the cloth in place in case of heavy winds. The black circle is called and oghal. This head gear have been proved effective for hot climates, and is equally effective as a defensive weapon.
A shmag can be rounded up and converted into a strong whip to whip people around in case of a fight. The oghal is equally effective and a whipping weapon.