Final answer:
Precedent, also known as stare decisis, is the legal principle that previous court decisions should be followed in similar cases. The Supreme Court upholds the ruling of a lower court by following a precedent. Precedent provides consistency and stability in the legal system, but it can be changed or overturned based on changing circumstances.
Step-by-step explanation:
Precedent, also known as stare decisis in Latin, is the legal principle that previous court decisions should be followed when deciding similar cases in the future. When the Supreme Court upholds the ruling of a lower court, it is following a precedent. Precedent provides consistency, certainty, and stability in the legal system. However, it is not absolute, and new precedents can be created or old ones can be overturned based on changing times and circumstances. For example, the landmark case Plessy v. Ferguson (1896) upheld the precedent of a lower court, but it was later overturned by the Supreme Court in Brown v. Board of Education (1954).