So, the term "hacker" and "hacking" has traditionally meant someone who is exploring the limits of systems (whether computer-based on otherwise) in a playful manner, often finding "clever" ways to make the system behave in unintended ways. The term is arguably even broader than that — see the Wikipedia entry on Hacker Culture[1] for more. The use of "hacker" to mean the exploitation of computer systems is more recent, and was traditionally referred to as "cracking". The two terms do have a decent amount of overlap, but the latter is much more commonly associated with malicious intent, whereas hacking really just means that a desire to push systems to their limits and see what kind of cleverness you can pull off!

[1]: https://en.wikipedia.org/wiki/Hacker_culture