Kanwar Saheb is a term used to show respect to a person who is considered to be an expert or a leader in the Sikh community. Think of it like being called "Mr. President" when referring to the leader of a country.
This term is often used specifically for someone who has studied the Sikh scriptures, teachings and history extensively and has a deep understanding of them. They are respected for their knowledge and often consulted for advice and guidance in matters related to Sikhism.
Overall, Kanwar Saheb is a way to show honor and respect to someone who is recognized as a knowledgeable and wise leader in the Sikh community.