The Malay term orang laut literally means the sea peoples. The Orang laut live and travel in their boats on the sea. Another Malay term for them, Orang Selat (literally Straits People), was brought into European languages as Celates.
Broadly speaking, the term encompasses the numerous tribes and groups inhabiting the islands and estuaries in the Riau-Lingga Archipelagos, the Pulau Tujuh Islands, the Batam Archipelago, and the coasts and offshore islands of eastern Sumatra, southern Malaysia Peninsula and Singapore. 
Historically, the orang laut played major roles in Srivijaya, the Sultanate of Malacca, and the Sultanate of Johor. They patrolled the adjacent sea areas, repelling real pirates, directing traders to their employers' ports and maintaining those ports' dominance in the area.
In the story "The Disturber of Traffic" by Rudyard Kipling, a character called Fenwick misrenders the Orang laut as "Orange-Lord" and the narrator character corrects him that they are the "Orang-Laut".