Mendelian inheritance is a set of principles that explain how traits are passed from parents to offspring. It is based on the work of Gregor Mendel, who conducted experiments with pea plants in the 19th century. Mendel discovered that traits are determined by discrete units called genes, which come in different forms known as alleles. Mendel's laws include the Law of Segregation, which states that each parent contributes one allele for each trait, and the Law of Independent Assortment, which explains how different traits are inherited independently. These principles form the foundation of modern genetics.