OptaPlanner is an open-source constraint solver designed to optimize planning and scheduling tasks. It provides a framework for solving complex optimization problems such as employee rostering, vehicle routing, task assignment, and resource allocation. Built on Java, OptaPlanner employs heuristic and metaheuristic algorithms to find efficient solutions for NP-hard problems, integrating seamlessly with Java environments. Users can benefit from its flexibility and scalability, catering to both small-scale and enterprise-level applications.