Common question, what is the difference between a 9006 bulb and a 9005 bulb? Really the difference is minor:
9006 bulbs are usually lower wattage when it comes to Halogen bulb: 80W vs 100W
9006 bulbs are used for low beams on many cars and 9005 on high beam.
9006 and 9005 plugs are slightly different with minor plastic tab making them different. See attached image.
For HID bulbs, 9006 and 9005 bulbs are indeed identical, since wattage is not the factor.