I did not even know that myself but if you google "canada immigration adr acronym" you get ADR=Alternative dispute resolution at
http://www.irb-cisr.gc.ca/Eng/brdcom/publications/oveape/Pages/index.aspx and there is says:
What is alternative dispute resolution?
The IAD may suggest that your appeal be decided through alternative dispute resolution (ADR). ADR is only suggested for appropriate cases. If you agree to ADR, this means that you will sit down with a dispute resolution officer, assigned by the IAD, and Minister's counsel to discuss your case. The dispute resolution officer will help you clarify the issues in your case and encourage both sides to agree on a decision about your case. This may mean that Minister's counsel agrees that your appeal should be allowed, or it may mean that you agree to withdraw your appeal. Alternative dispute resolution does not work for every case, so if you cannot all agree your appeal will return to the IAD for decision.
So now we both know.