What exacly is hacking?
It falls under different categories, however generally the term is used to reference programmers or scripters who manipulate a website or a game to work in their favor, in violation of the rules of the site normally. Example, changing your currency on a game to 1000 coins when it is legally only supposed to be 10 coins, for instance. Skiddies is a term used to reference non-programmers who use another person's app to do this, then claim to be expert hackers. In reality, they know about as much relating hacking as a 5 year old does.
The technology term for breaking the rules of a certain system. For instance, trying a ton of administrative passwords to get privileged access to a server without permission would be one way.