When the subject of Hackers and Crackers come up, people often intermingle the two terms and mistakenly use hacking and cracking as the same term. Although the two terms have some significant similarities, the main motive behind hacking and cracking are completely different.
Hackers (also known as "white hat" hackers) modify and add code, thus changing the code so that it does something other than what it was originally intended for. For example, a website owner may hire a programmer to "hack" or alter the code of their online store to perhaps add a shipping module that was not there before. Hackers usually have a bad reputation, but hacking skills in itself can be helpful and useful if used for positive reasons. Many people hack their own systems, or get permission to hack someone else's, to gain more knowledge regarding the security of their website or to have their website do some feature it didn't have before….hacking the code would be less expensive than buying new software to acquire a new feature you did not have before. There are people who actually have jobs as professional hackers (ethical hackers) who are hired by companies to test and repair security systems by hacking into them. It's legal to hack in these cases because fraud, stealing, or other criminal acts are not being committed. Hackers can be helpful in that they have the ability to alter and take advantage of computer systems, using their skill set to suppress cracker activity.
Crackers, also known as "malicious hackers" and "black-hat hackers", are different because although they have the same skills as a hacker, they use their power to commit criminal acts. For example, crackers can send viruses, steal personal information and commit other crimes using just their skills and a home computer. Obviously, the activities of most Crackers are considered illegal.
In comparing Hackers to Crackers, we can see that they have similar skill sets, but while Hacker activity is usually of the legal kind, Cracker activity is usually of the illegal kind.