It is pretty obviously really, take this huge digger at a big bucket on the front and those things that stick out of the bucket that lift things and dig into the ground are bucket teeth. OK that statement was tongue and cheek, but the quality of the work a digger has to do is reliant on the quality of its bucket teeth. These little units are not permanently welded to the bucket (in most cases), they are designed to be replaced at different times. so as not to replace the whole bucket. these bucket teeth can be bought in different sizes to suit small rubber tracked vehicles right up to these huge diggers we see on big building and excavating projects.
So to help understand what bucket teeth do, we have added a small video found on a third party site. Yu may not find this to be the biggest machine out there, but it is a good example of what bucket teeth actually do.