Though hackers are typically associated with being able to identify security issues with computers, software and databases, hacking can occur in almost any medium. A hacker is merely a person who sees a problem that needs to be solved and who creates a unique solution which he then freely shares with the rest of his community.
In fact, what true hackers do has nothing to do with exploiting technology to harm individuals and companies. The group of people who use their knowledge of software and technology to deface websites, deploy malicious programs and otherwise "break" things are, in the hacker world, derisively referred to as "crackers" or, even more simply, criminals or vandals. Crackers break or destroy things, while hackers build upon and improve things.
That doesn't mean, however, that question of what hackers do isn't complicated to answer. Being a hacker is much like being an engineer and, in fact, many hackers refer to themselves as social engineers. Engineers all have a similar set of skills, but not all choose to use those skills the same way. While some will choose to help the public by doing things like designing bridges, others will use those skills for less philanthropic endeavors, such as designing weapons. Hackers, too, have a common skill set and while some hackers may use them to wreak havoc, true hackers use those skills to find and identify vulnerabilities that need to be fixed.
This skill set isn't easily defined, though, for the most, part hackers are well versed in basic programming languages like Python, C and Java. Many hackers have an excellent understanding of how things work and are put together. Whether that means machinery or social systems, a hacker often has an uncanny ability to see how all the parts of something are dependent on one another and how changing one of those parts can improve the whole.
There are all kinds of hackers. There are those who hack for fun, looking for bugs as they try out new software, applications and technological devices. These are the people who are able to find encoded Easter Eggs in video games and who take apart and re-build mobile devices to make them faster and more efficient. There are criminals, who hack for personal gain. These are the people who may find a backdoor entrance in the code to a database, allowing them access to financial information, which is then used maliciously. But there are also other hackers, those who make software and applications safer for the public. Sometimes known as "tiger teams" or "white hat hackers," these are people hired by large corporations to try to find security issues with software before its general release.
Tiger teams have the potential to be of assistance to everyone. Not only do these hackers provide software developers with a new set of eyes, but in trying to find loopholes in code and deployment, tiger teams also create solutions. These solutions can be applied to distributions before release, saving companies the headaches of consumer complaints and compromised safety, or the solutions can be released as software patches. That allows consumers to fix bugs and know their information is more secure.
Consumers benefit from hackers on a more personal level, too. Since most hacking is done in the field of computer programming and most hackers believe in freely sharing information, hackers have created huge repositories of open-source software. This allows consumers to use non-commercial software with features comparable to a commercial version. OpenOffice, for example, rivals Microsoft Word and is distributed freely. Since the source code is available, it's also continuously improved upon by hackers all over the world. Many Linux distributions, including the K12 Linux Terminal Server Project, are used to help school districts save money that would have to be spent on software licenses.