Hacking refers to the act of exploiting vulnerabilities in computer systems, networks, or software to gain unauthorized access, often with malicious intent. Hackers may use various techniques, such as exploiting security flaws, phishing, or deploying malware, to infiltrate systems and steal, modify, or destroy data. While hacking is often associated with illegal activities, it can also refer to ethical hacking, where security experts test systems to identify and fix vulnerabilities, thereby improving cybersecurity.