The primary function of a load testing tool is to assess how a system behaves under various levels of user demand and ensures it can handle expected traffic loads. This type of tool simulates multiple users interacting with an application simultaneously, identifying performance bottlenecks and potential points of failure. Load testing helps developers gauge system responsiveness and stability, allowing for improvements before deployment. It is essential for applications to maintain performance standards during high-traffic events, such as product launches or sales, ensuring a positive user experience and minimizing downtime.