Although this has already been explained elsewhere on the site, this is a question i've noticed that has come up lately. This shall be a relatively short post.
''What is the difference between magick and magic?''
Magic, without the K, is a reference to the magic you see on stage. For example, a magician pulling a rabbit out of a hat, or vanishing into thin air.
Magick, on the other hand, usually refers to the magic many of us on this site practice; such as casting a spell, for example.
Personally, I do not bother with the K, as I feel on a site dedicated to the second one of the two people will understand which variation I am making a reference to.
However, many use the version with the K. It is no cause for worry.