Final answer:
Precedent is an earlier decision used to guide future court cases, and stare decisis is the principle where courts stand by these earlier decisions to ensure consistency and legitimacy in the legal system.
Step-by-step explanation:
An earlier legal decision that should be used as a guide or rule for future cases is known as a precedent. The legal system uses the principle of stare decisis, which translates to "let the decision stand," to ensure that decisions in new cases are consistent with similar cases decided in the past. This principle is crucial in the common law system where it contributes to legal certainty and the legitimacy of court rulings. The Supreme Court also relies on precedents when making rulings, although there are occasions where it may override past decisions to address justice matters, such as human and civil rights issues.