An advisor is a qualified business expert in one or more fields. For example, an advisor could be an expert in financing and/or sales.
Advisor is also a generic term we use for the roles of mentor and coach. In both cases, the individual has been independently qualified by us. The differences between being a coach and being a mentor is explained here.
For most people, the major difference between the two roles is that a coach is paid for their feedback and advice while a mentor is not.