Well do you mean ethically or something closer to an actual definition. People will tell you it's meant as a way of helping those around you or as knowledge of the few to fulfill the needs of the many, but even if you believe that's what it's meant for then you may or may not be right but you can't deny that it is also a force used for harm, destruction, and selfishness as well. If you mean like how it works the answers will vary and no offense to any one but many don't even know what they're talking about especially when they say energies. I'm not claiming that I know (though I do have my own ideas) but some will just use pseudo science that is really just gibberish and they didn't really state anything or even know anything about what they're saying.
And here's one that just poped into my head though I'm not sure if it's true. Functions of consciousness and the universe that can not be tested through the scientific method. :p
I find magic a alteration of chance through manipulating the energy of the universe, and as for use its just a nother meens to a reason, or however that saying goes
I agree with guardleone. It is knowing how to alter chance, probability, and
direct already existing energy in a desired direction. It is also a way to
connect with said universe. But outkast makes a valid point also. Depends
on what you believe, practise, and who you are fundamentally.
Most of the above posts are about spell casting; not magic! They are about using magic, not magic itself.
Magic is all around you! Magic is happening all the time in Nature. Every day species become extinct, and new species take their place.
Life itself is "magical". Plant a few seeds in good soil; add water and sunshine, Watch the tiny seeds grow into tall plants, and then produce more seeds! How much "magic" do you want?