Hacking can be difficult and there are many different ways to hack and many different exploits to use. Hacking is neither defined nor limited by exploitation or exploration. Hacking into someone else's system may be illegal, so don't do it unless you are sure you have permission from the owner of the system you are trying to hack or you are sure it's worth it AND you won't get caught.

Hacking was primarily used for learning new things about systems and computing in general, 'in the good old days'. In recent years it has taken dark connotations and in general has been looked down upon. Likewise, many corporations now employ "hackers" to test the strengths and weaknesses of their own systems. These hackers know when to stop, and it is the positive trust they have built that earn them large salaries.

There is a major difference between a hacker and a cracker. A cracker is motivated by malicious (namely: money) reasons; a hacker is attempting to gain knowledge through exploration, at any cost and in any way - not always legal. Along with the permission, you NEED TO HAVE a written consent showing proof that you got permission from that person or company.