Funny that you ask, it's good that you ask, I don't know if you can write in all caps or not but I won't risk it:
I'm finally able to put this in a forum, spells do not make snow fall in summer or change your exam results from 6 months ago, yes I have had requests for both, and it doesn't even snow where I live. Magic does not defy the universe. Nothing works that way.
good, with that out of the way...
Magic is, in a practical sense of the world today, a form of craft beyond the physical, some do it because it gives them what they want, others do so because it is a part of their beliefs, others do it for both. Now, the main thing is our focused intent, focusing it, giving it essence, material, all that. But if you go back in time, humans discovered that chants, dances, colors, scents, herbs and geometries can help us manifest and focus on our goals and desires, so came the spells. They are means of better focusing our energy into our desires and wishes.