A hacker is someone with advanced computer skills who explores how computer systems and software work, often by finding ways to access or modify them that weren't originally intended. The word can describe very different types of people depending on their intentions.

Some hackers use their skills constructively. They might work for companies testing security systems to find weaknesses before criminals can exploit them. These ethical hackers help make websites, banks, and computer networks safer. A company might hire hackers to try breaking into their own systems so they can fix any vulnerabilities they discover.

Other hackers break into computer systems illegally to steal information, cause damage, or commit fraud. These malicious hackers might steal credit card numbers, spread computer viruses, or break into private accounts. When news reports mention hackers stealing data or shutting down websites, they're usually referring to this criminal type of hacking.

The word can also describe someone who creatively modifies or repurposes technology in clever ways. A tinkerer who figures out how to make their video game console do something new might be called a hacker in this more playful sense.