A hacker, in the context of programming, is an individual who uses their technical skills to explore and manipulate computer systems and networks. Hackers can be categorized into different types, such as white hat hackers, who work to improve security, and black hat hackers, who exploit vulnerabilities for malicious purposes. Their activities can range from ethical hacking to unauthorized access. Hackers often possess strong knowledge of programming languages, operating systems, and network protocols. They may create software, develop security tools, or find and report bugs in systems. The term "hacker" can have both positive and negative connotations, depending on the intent behind their actions.