Magic is a force of nature, and an artifact of either spirit or the divine, depending on your preferred vernacular. Traditions around the world hold that angels or other great beings originally taught magic to humans in the distant past. True or not, the latter is an apt metaphor for the discovery of such a marvelous thing.
When I was very new to the art, the definition I liked was:
Magic is the science and art of causing change to occur in conformity with the will. This change may be subjective (change to your consciousness), objective (change in the real world), or (most often) both.
This definition is the distilled result of something written by Crowley, improved by Fortune, and finally polished by the Golden Dawn. In a technical sense it is definitely correct. The above is as good an explanation as you’ll find on what magic, as an active endeavor, is.
Magic is Somehow More, Yet Difficult to Grasp
Perhaps not now, in the beginning, but certainly the more time you spend with the Great Arcanum, it will become clear that something more is in play here. A force, sure. Art, ok. An effect unexplainable by academic means and measures, yes.
Still, absolutely there is still more to the story of what magic is.
To put this into perspective, the second (or third?) time I picked the study back up, having abandoned it once or twice in my youth, I did so to answer some of those nagging questions: Is there a thing called God, truly? Is there a soul or spirit to me, and do I go on after this life?
Within a year of deep and rigorous study I had to admit, for the sake of intellectual honesty, the answer to these inquiries, at least it seemed clear, was YES. I don’t recall the questions I sought out for the second year, as many annual cycles have passed since then and the memory of a magician is no better necessarily than the memory of any other person once enough age has passed onto it.
The best advice I can give is to follow the simple course on this site and find out for yourself exactly what magic is and isn’t.
I’ll leave you with one of my more poetic ideas, in saying magic is a connection you can make with a deeper part of yourself that is connected to every other part of you and to every other person, place, or point of time in your life and in the world as a whole. From this connection spring many wonderful possibilities and many opportunities to be amazed.