The answer by pohnpei is excellent. You may want to connect the explanation of historical significance to the significance of indentured servitude apparent today. 

Indentured Servitude is Contractual labor exploiting labor for financial and personal gain or from duty.

The word "slavery" is used when we consider the very serious and epidemic problem of mdern day slavery, which is called human trafficking. We like to distinguish slavery and indentured servitude when teaching history. However, the term "indentured servitude" is a form of human trafficking in our modern world.

That indentured servitude is a form of slavery does not mean that people throughout history did not willingly sign a servitude contract and sometimes find great success in the indenturing process. 

What is the economic and social impact of modern day servitude? Contractual Servitude impacts U.S. and global markets through human exploitation. 

In history, women, children and men came to America in exchange for free passage, in order to pay a debt, for new opportunities, for hope and to escape oppression. The modern world economy still benefits from free or cheap labor and servitude exploited workers lack control over their lives and human rights. Indentured servitude still exists today as well as Slavery.  

So, what is the historical significance of indentured servitude? It never ended and servitude contracts continue today and are fulfilled by deaths and tragedy more often than by fresh starts through new opportunities.  

Indentured servants were historically significant in the American colonies for at least two main reasons.

First, indentured servants were the original backbone of the economy in the Chesapeake colonies.  In the early days of the colonies, there were not enough people who were willing to work for wages in the Chesapeake colonies.  Therefore, indentured servants were brought over from England.  These servants were essentially enslaved for a period of time (often 7 years) in exchange for having their way to the colonies paid for.  After the term of the indenture, they were free.  People who accepted this deal were the main part of the labor force for the Chesapeake colonies early on.

Second, indentured servants were the precursors to African slaves.  The use of indentured servants made people in the Chesapeake accustomed to the use of unfree labor.  When there started to be problems with attracting and retaining indentured servants, landowners turned to African slavery.  This, of course, was of tremendous significance for US history.