In legal terms, a precedent is an event or legal decision that other judges follow when similar cases are presented in the court room.
Judges use these prior cases to be the baseline of their rulings in current cases. If the precedent hasn't been overturned by a higher court or more other more relatable, recent decision, then the precedent is legally binding and judges should follow and apply the prior ruling to their own case.
For example, there were four court rulings (1938-1950) that laid the foundation for ruling in favor of school desegregation before Brown vs. The Board of Education in 1952. These rulings helped this case go all the way to the Supreme Court, who ruled that "separate but equal" in schools or anywhere based on race denied people equal protection under the Fourteenth Amendment, as well as their right to due process, under the Fifth Amendment.
