Bondo....is actually a brand name not a description of material. If you were asking about that, it's basically an automotive compound used in filling gaps and dents while doing body-work on a car or vehicle. That's long winded and we've just shorted it to "Bondo" so I guess it just has become common knowledge. There are many different car filler compounds out there, but we still refer them all as Bondo.....the end result is the same and no one better than the next. For me.....Bondo is more readily accessible since it is sold in all major DYI home-centers like HomeDepot, Ace, and Lowe's just to name a few.