ArgoUML is a free and open-source UML modeling tool that supports all standard UML diagrams. It allows users to create, edit, and visualize UML models and diagrams with its intuitive interface. The software also includes a code generator that can generate code in Java, C++, and other programming languages based on the UML models. Additionally, ArgoUML supports collaboration features, making it possible for multiple users to work on the same UML model simultaneously.