Standard lighting using a filament which glows when a current is put through. Incandescent bulbs can be large (C9) or small (mini-lights).
What Causes Incandescent Bulbs/Strands to Not Work?-Missing Bulb(s)
-Bulb Wires not making contact or not seated properly
-Bulb wires broken off
-Shunt insulation did not burnt off properly