Incandescent and halogen appear the same to these switches. Basically, if the fixtures has a ballast or the lamp uses gas for illumination (as opposed to filament) it will require a special dimmer made expressly for that use or no dimmer is permitted. Such lamps would be fluorescent, compact fluorescent (aka CFL), high pressure sodium, mercury vapor, etc.

There are also some DIMABLE CFLs on the market. These can be used with ordinary dimmers and require no special wiring. Simply remove the old incandescent and replace with a dimaable CFL. Be sure to read the package for any limitations. Keep in mind, the CFL package must state it is dimable, as not all are. Dimable CFLs cost more than the non-dimable types.

Even though it was not asked, never use a dimmer to control the speed of a fan. That applies whether it is a paddle fan or a table fan plugged into an outlet that is controlled by a dimmer switch. There are variable speed motor controls made for this purpose.

I hope this helps & good luck!