Sympathetic magick is a so called "primitive" form of magick which follows the idea that if something looks like something else, it has a "magickal link" with it. In addition, if something comes from something else it retains a "magickal link" with it.
The practice of sympathetic magick involves the enacting of symbolic or real acts on the object which has a magickal link with the desired target of the acts. This includes, but is not exclusive to, fetishes and "voodoo dolls" which are, incidentally, used in both love and hate magick. An element of sympathetic magick may be useful in any physical "results magick" since it creates a stronger link between the ritual and the desired result.