Schubert varieties are specific types of subvarieties in algebraic geometry, associated with the study of Grassmannians. They are defined using Schubert classes, which represent certain geometric conditions on linear subspaces. Each Schubert variety corresponds to a particular arrangement of these subspaces, allowing mathematicians to explore their properties and relationships. These varieties play a crucial role in various areas of mathematics, including intersection theory and representation theory. They help in understanding the structure of flag varieties and have applications in mathematical physics and combinatorics. The study of Schubert varieties reveals deep connections between geometry and algebra.