Which of the following best describes exploratory testing?

Exploratory testing is best described as an informal test design technique that is controlled by the tester. This approach emphasizes the tester's skills, creativity, and intuition rather than relying on formal test cases or scripts. Testers explore the application actively, often simultaneously designing and executing tests based on their understanding of the system and its functionality. This method allows for greater adaptability in uncovering unexpected issues, as testers can respond in real-time to the behaviors they observe.

Other options do not accurately capture the essence of exploratory testing. For instance, describing it as a structured approach to automated testing suggests a process that depends heavily on predetermined scripts and automated tools, which contrasts with the flexibility inherent in exploratory testing. Similarly, calling it a formal test design method implies a rigidity that is not present; exploratory testing thrives on spontaneity and individual tester insights. Lastly, suggesting that it is focused solely on performance testing is misleading, as exploratory testing can apply to various testing types, including functional, usability, and more.