What is the concept of an indentured servant?

Indentured servitude is a system where the wealthy can obtain unfree laborers in exchange for a fixed fee. It was most used in combination with slavery in colonial America to obtain laborers for large landholders. British citizens (and other potential immigrants) who wanted to emigrate to the colonies were often unable to pay the costs of passage. These emigrants would then need to seek out an employer in the colonies. This employer would pay the cost of passage in exchange for a fixed period of servitude from the immigrant. This period of servitude was akin to slavery, though the indentured servant did later receive additional protections.
Indentured servitude was not always voluntary. In England, there was a desire to end the use of the death penalty for many crimes that were classified as felonies despite being relatively minor in terms of the harm committed. In order to prevent an explosion in the prison populations, a new punishment was instituted. This new punishment essentially exiled convicts to the colonies for a fixed term. These convicts, upon arriving in the colonies, would be sold as indentured servants at auction in order to pay for the costs of passage and any other debts that needed to be settled. At the end of the convicts's term of service, they were permitted to return to England (at their own cost) or to remain in the colonies.
Indentured servitude fell out of favor in the colonies for two reasons. First, the initial cost of obtaining an indentured servant was high and the term of service was fixed, sometimes with an additional grant of land or money at the completion of service. The lack of a term of service for slaves made them the more attractive option for the purchase of laborers.
Second, indentured servants often served alongside slaves. The hardships of servitude were experienced by both indentured servants and slaves, leading to camaraderie among these groups in the colonies. On several occasions, indentured servants and slaves would engage in unified uprisings that created hardships for the ruling class of the colonies. The unity between slaves and indentured servants was broken by granting leniency for rebellion to indentured servants (who were generally white) while retaining harsh penalties for slaves (who were generally African). Indentured servants were also granted additional protections in order to enhance the differences between the states of slaves and indentured servants, though this also lowered the value of indentured servitude to the wealthy. Ultimately, wealthy landholders switched from a mix of indentured servants and slaves to the sole use of slavery.