Indenture is a concept closely related to indentured servitude in which a person is contracted to work without pay for a certain number of years. The contract, called indenture, may be entered into voluntarily for later compensation or repayment or imposed as a judicial penalty. Historically, it was used to pay for an apprenticeship when an apprentice agreed to work for a master artisan for free in order to learn a trade. Later, indentures were also used as a way to pay the cost of transportation to the colonies in the Americas.
Like any loan, the indenture could be sold. For example, most employers had to resort to intermediaries to hire and transport workers, so bonded slaves were usually bought and sold upon arrival at their destination. Like enslaved prices, their value went up or down depending on supply and demand. When the indenture (loan) was paid, the worker became free. Sometimes they could be given a plot of land. Usually, the indentured laborers could marry, move about as long as the work was done, read whatever they wanted, and attend classes.