Edited from:
http://www.cognitivecoaching.cc/whatwearelearning.htm

“ . . . the . . .  coach is non-directive, using data and reflective questions to support and develop the teacher's cognition related to the learning processes of students. Advice and judgments are withheld. [Mentoring]* can involve such things as working with student data, planning common curriculum implementation, or problem-resolving related to student achievement gaps.

The [mentor] collaborates with individuals and teams. Collaboration differs from . . . Coaching in that it is shared work around common goals. The collaboration may include planning, brainstorming, analyzing, and even advocacy.

As a consultant, the [mentor] brings expertise to any given situation. At times the [mentor] serves as a trainer or as model for an instructional strategy. Consulting differs from coaching in that this function includes providing rationale and giving advice. On a given day, the [mentor] makes choices about when to coach, when to collaborate and when to consult. The decision-making process is complex and requires thoughtful differentiation based on the needs of the teacher . . .  being served.”

An outstanding article relating mentoring to these three “Cs” can be found at:
http://www.bham.wednet.edu/departments/currdept/profdev/pdcoach.htm

*The words and acronym “Building Resource Teacher (BRT)” have been replaced by “mentoring” or “mentor” for purposes of this information.