Nolvasan- Commercial name for Chlorhexidine diacetate. A topical antiseptic used to clean, disinfect, and treat external cuts or wounds on animals. Available in liquid and ointment form. From what I can tell, it is similar to Neosporin or Bacitracin...
Chlorhexidine Gluconate- Antiseptic/ disinfectant commonly used in oral rinses to treat gingivitis.
I imagine the reason Nolvasan is more expensive is possibly because of other ingredients added to it to make it more of a medical grade product...