SoapUI is a free and open-source test automation framework for APIs like SOAP and REST. Its functionality includes web service inspection, invoking, development, simulation and mocking, functional testing, load and compliance testing. It is also offered as a paid pro version, which has advanced features like test history, SQL query builder, and enhanced support.

SoapUI's strengths are its easy setup, well-designed user interface, and breadth of integrations. It is simple to learn and operate even for non-technical users. However, it can be slow and the free version lacks important features like version control.