The Seventh Amendment is important because it helps ensure fairness in our justice system. Specifically, the Seventh Amendment ensures the right to a trial by jury in civil court cases at the federal level. Unlike criminal cases, in which the government prosecutes the case, civil cases are disputes between two or more individuals, organizations, or companies.
The actual text of the amendment reads as follows:
In Suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise re-examined in any Court of the United States, than according to the rules of the common law.
To paraphrase, this amendment says that for any civil case dealing with an issue in which more than twenty dollars is at stake, those involved have a right to a trial by a jury of their peers. It also says that no court or judge can later re-examine the jury's finding and overturn it (with a few exceptions).
If there was no right to jury trial, these sorts of civil disputes would likely have been settled by a judge. When the Bill of Rights was being drafted, Anti-Federalists pushed for the inclusion of the Seventh Amendment because they felt that leaving these cases solely in the hands of a judge would give too much power to the government. They believed the right to a civil jury could help protect litigants against bad laws and biased or corrupt judges.
It is important to note that this amendment only ensures a jury trial for civil cases at the federal level, though most state constitutions have provided for this right at the state level as well.