Unified Modeling Language (UML) is a standardized visual language used in software engineering to create diagrams that represent the design and architecture of a system. It helps developers and stakeholders understand complex systems by providing a clear and organized way to visualize components, relationships, and behaviors. UML includes various types of diagrams, such as class diagrams, use case diagrams, and sequence diagrams, each serving a specific purpose. These diagrams facilitate communication among team members and assist in documenting the system's requirements and design, making it easier to manage and develop software projects effectively.