A Cracker, which is a more politically correct term than Hacker, is a person who performs a cyberattack.
Their purpose is to attack (essentially for personal interests) servers and IT systems, in order to extort data and affect the privacy or welfare of an individual. They are usually hired by certain firms and companies for industrial espionage, upon payment.
A Hacker, unlike a Cracker, is a person who has similar computer skills, but different intentions. It means that his work is not based upon deceit or blackmail. On the contrary, a Hacker tries to discover the vulnerabilities of an IT system, in order to safeguard and protect one’s data from cyberattacks. He is usually hired to test an IT infrastructure or to put to the test the safety of specific software.