Boundary conditions are specific constraints applied to a problem in fields like physics, engineering, and mathematics. They define the behavior of a system at its limits or edges, helping to determine how it will respond under various scenarios. For example, in a heat transfer problem, boundary conditions might specify the temperature at the surface of an object. These conditions are crucial for solving differential equations, as they provide necessary information to find unique solutions. Without proper boundary conditions, the results may be ambiguous or incorrect, making them essential for accurate modeling and analysis in scientific and technical applications.