A charm can be anything - an object, a word, or a symbol that's believed to have inherent or given magical powers. Charms often combine an incantation with a symbolic object because the verbalized element works in tandem with the practionner's will, wrapping the object in energy that gets abdorbed into it's matrix. The magic changes the charm's basic energy patterns to match the desired pattern. (though the chage usually isn't permanent)
Verbal Charms: recited at the moment when the practionner needs it to manifest. It's often repeated a symbolic number of times to re-emphasize the will of the practionner and supper the vibrations of the incantation.
Written Charms: often has a symbolic shape or color. Generally, activating the charm only requires carrying it, however, if the charm consists of a series of written words, then practionner might repeat those words and touch the charn as a means of triggering it.