There are various types of hackers today, but the traditional meaning of the word hacker is someone who spends a large amount of time in exploring and figuring out how the wired world works. Today, however, this word is mainly associated with computer criminals who intrude computer networks and violate the law.

Old School Hackers

These are highly skilled professionals who often hire out their skills to organizations concerned about their own network’s safety. They represent hackers of earlier generation. Many of these purists want the criminals, who break into computers to be called "crackers" rather than "hackers".

Internals

These are either employees dissatisfied with the company managment or ex-employees who know the company’s security “ropes”. They use their knowledge about the internal company routines and hack into computers to have their way.

Cyber punks

The stereotypical image of hackers, they are usually antisocial, socially inept, and burdened with angst directed towards the real world which was unfair to them. This anger finds its channels in cyberspace. Understandably, they relate better to computers than people and are more than capable of writing their own malicious programs. They are usually guilty of committing damaging acts such as spamming, credit card number theft, defacing web pages, etc.

Professional Criminals and Cyber Terrorists

Clearly the most dangerous, ex-intelligence operatives and professional criminals are basically, guns for hire. They have access to state of the art equipments, are extremely well trained and specialize in corporate espionage, causing widespread yet controlled damaged in their wake. Those with greater professional pride are not interested in disrupting systems but more on stealing intelligence data.

Newbies and Script Kiddies

These are people (usually teenagers) who want to be recognized as dangerous hackers but lack miserably in the required determination and skills. They use ready-made cracking programs (made by others), intending to cause damage to and corrupt systems. They are almost always caught because they brag their exploits online just to get attention.

The list of motives is endless: addiction, illicit thrill, low self esteem, boredom, and a desperate need for recognition from the hacker peer group, all cowardly actions performed under the protection of anonymity.

Reference

New Order - computer security and networking portal
http://neworder.box.sk/newsread.php?newsid=4181

Hacker Psych 101 By Jeremy Quittner
http://tlc.discovery.com/convergence/hackers/articles/psych.html