What is a gum biopsy and what does it tell you?

Sampling. The gum is part of your mouth (around the teeth). A biopsy of it is usually done to try and document a specific disease or process. There are hundreds of reasons to do a biopsy, so you should probably wait for the pathologist to give you a result before you move further forward in the process.
Plenty of info. Biopsy procedure is performed by trimming off a sample of gum tissue which is sent to a laboratory for evaluation by a specialist who can determine if the cells in the sample are normal or if there are problems (like oral cancer or per-cancerous) and if any corrective action is necessary. Talk to your dentist or oral surgeon for further details.