what is a h3 bulb?

I was going to order a new set of bulbs for my headlights, and one comes with the 9005 size (high beam) and 9006 (low beam) along with a "H3" bulb. What is this "H3" bulb and why would i want it?

I don't know what kind of headlights you are putting these bulbs in but h3 bulbs are smaller bulbs that are commonly used in fog lights and aftermarket projector headlights. the are quite a few different size bulbs, h3 is just a different kind of bulb than 9005 or 9006. there are h1, h3 9004, 9005, 9006,9007 and even h7 bulbs that are commonly used in most headlight applications today, aftermarket and oem a like.

Ok thanks, looks like I won't end up needing that bulb. Thanks for the help