See also H-1B program for a modern version.
Indentured servitude consisted of a worker (the "indentured servant"), usually from a foreign country, agreeing to work for a specific time, usually about 7-8 years, to pay off his costs of travel to the new country. Pay would be minimal during those 7-8 years, and might only include housing, food and training. The worker might also receive land for himself at the end.
Indentured servitude was most popular in the early Virginia colony in the 1600s, when many workers were needed to farm tobacco. But a violent uprising by indentured servants in the Virginia colony, known as Bacon's Rebellion, made indentured servitude unpopular.
The term "indentured" comes from the type of legal contract that the employer and employee would sign (an indenture), obligating the employer to pay the cost of passage across the Atlantic and provide room and board while the servant was obligated to work for up to seven years.