These mentors are only examples. There can be many more different types of mentors. Look around your workplace, your life, and see who is an expert that you can learn something from.
In the sub-groups of formal and informal mentoring relationships: peer mentoring relationships are relationships where individuals are at the same skill training, similar positions and stages of career. However, one person may be more knowledgeable in a certain aspect or another, but they can help each other to progress in their work. A lot of time, peer relationships provide a lot of support, empathy and advice because the situations are quite similar.
Situational mentoring: Short-term relationships in which a person mentors for a specific purpose. This could be a company bringing an expert in regarding social media, or internet safety. This expert can mentor employees to make them more knowledgeable about a specific topic or skill.
Supervisory mentoring: This kind of mentoring has 'go to' people who are supervisors. These are people who have answers to many questions, and can advise to take the best plan of action. This can be a conflict of interest relationship because many supervisors do not feel comfortable also being a mentor.
Mentoring circles: Participants from all levels of the organization propose and own a topic. They then meet in groups to discuss the topic, which motivates them to grow and become more knowledgeable. Flash mentoring is ideal for job shadowing, reverse mentoring, and more.