The Washington tree, located in the Giant Forest Grove in Sequoia National Park provides a good example of the aforementioned phenomena. This tree was the second largest tree in the world (only the General Sherman tree was larger) until just a few years ago.
A halogen is a representative element from group VII in the periodic table. More specifically, Fluorine, Chlorine, Bromine, Iodine, and Astatine. Astatine is a very unstable radionuclide so is not normally dealt with. A halide is a chemical compound of halogens bonded to more electro positive elements.
Halogens are just incandescent bulbs with a bit of halogen gas trapped inside with the filament. This gas helps recycle the burned-up tungsten gas back onto the filament, making for a slightly more efficient light. Unlike the mercury in CFLs, this gas isn't anything that could be classified as hazardous waste.