Dred Scott v. Sandford is one of the most important Supreme Court decisions in U.S. history. It was a key part of the political turmoil of the decades leading to the Civil War, although the decision was ironically motivated in part by a desire to halt unrest over slavery. Quite simply, the 6-3 decision handed down in 1857 declared that black people were inferior to whites, weren't and couldn't be U.S. citizens, had no right to file federal lawsuits, and were property that couldn't be taken from their owners without due process. Furthermore, western territories could no longer ban slavery, and slaves brought into supposedly free territories were not, in fact, freed.
Scott was a slave whose owner had moved frequently as a result of his position in the U.S. Army, living in free territories at times. Scott attempted to sue for freedom based on that fact. He lost, but the case wound its way through various appeals for years. Scott was owned by the executor of his former owner's estate, a man named John Sanford (the Supreme Court spelled his name incorrectly in their documents).
The 13th and14th Amendments overturned the Dred Scott decision, but could only be enacted after several years of bloody Civil War. The 13th Amendment simply bans slavery in the U.S. The 14th amendment covers a lot of ground, but the relevant portion states, "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws."