Dothraki

The Dothraki are a race of nomadic warriors in Essos, the vast continent to the east of Westeros. They ride horses and are said to be born, fight and die in the saddle. They are formidable warriors known for their curved swords, the arakhs, their use of whips in battle and their use of huge, recurved bows with impressive range and striking power that can be fired from horseback.

In the books
In the Song of Ice and Fire novels the Dothraki are numerous and are divided into large hordes or khalasars which range over vast areas. Khal Drogo's khalasar consists of 40,000 warriors and is said to be unusually large. The Dothraki are mostly active on the Dothraki Sea, a vast inland area of grassy plains and steppes, but sometimes raid into the Free Cities to the west and Slaver's Bay and Lhazar to the south. The Dothraki are untrusting of outsiders, but respectful of capable warriors even from other cultures. They particularly dislike those who have inherited their titles and done nothing to earn them.