Halogen is the type of bulb technology - changes the gas & glass so that "stuff" that boils off the filament re-condenses back onto it most of the time - hence can have hotter filament (brighter/whiter) and no "gone dim from silver inside" problems. Easyish to tell if bulb is halogen: - will usually be cylindrical (gas is under pressure) - will be lots of warnings to not touch glass with fingers - (fingerprints can etch/distort the glass at high operating temps & cause ...
OK, for those that want to "fill their car" with what I'd recommend as fairly bog std crap for long-ish touring rides (ex the Chch Weds Night Rides thread after I reminded them that a tyre kit wasn't a bad idea and then someone did a clutch cable too & then they got all smart-ass): Yeah, well I do carry one of those too - don't want the 6-weeks-ex-germany-its-unobtainium-otherwise BS I'd get via Murphys' law if i didn't have one!... But I thought I'd already lectured the obvious too ...