A hacker is a person who uses computers to gain unauthorized access to data. There are many different types of hackers. There are white hat, grey hat, and black hat hackers. Some hackers are defined by their intention. For example, a hacker that attacks for political reasons may be known as a hacktivist. A white hat hacker has no criminal intent, but instead focuses on finding and fixing network vulnerabilities.
Often companies will hire a white hat hacker to test the security of their network for vulnerabilities. A grey hat hacker is someone who may have criminal intent, but not often for personal gain. Often a grey hat will seek to expose a network vulnerability without the permission from the owner of the network. A black hat hacker is purely criminal. Their sole objective is personal gain. Black hat hackers take advantage of network vulnerabilities however they can for maximum benefit. A cyber-criminal is another type of black hat hacker, who is motivated to attack for illegal financial gain. A more basic type of hacker is known as a script kiddie. A script kiddie is a person who knows how to use basic hacking tools, but doesn't understand how they work. They often lack the knowledge to launch any kind of real attack, but can still cause problems on a poorly protected network.