In Buddhism we usually think of a teacher. In Catholicism, the comparable term might be spiritual guide. Whatever term we use, this person has a crucial role in our spiritual growth. Role? Actually, it would be more accurate to say "roles". I came up with a list of nine, probably not exhaustive or comprehensive, but perhaps a good starting point. Here are brief descriptions, in no particular order.
Teacher
A teacher is a person who imparts to you a given body of knowledge, skill or capability. In the spiritual context, this might mean the underlying philosophy, moral principles, and meditation methods. A teacher has to have experience and knowledge to impart and, as a student, your responsibility is to learn from the teacher. The teacher may touch into coach or therapist roles, but only to a limited extent. Change in you comes through your efforts to learn what the teacher is teaching and to put it into practice.
Guru
A guru is a special teacher, a person whom you see as an expression of what it means to be awake and present and who also has the ability to elicit such experiences of awakening in you (i.e., transmission). In addition, he or she may provide instruction in methods of practice and guidance in both life and practice. Such a teacher may place significant demands on you to help you work through conceptual, emotional or spiritual blocks that prevent you from deeper levels of experience. Change in you comes through your confidence (or devotion) to your guru. This allows a deep emotional relationship to form which becomes the means by which you open to deeper levels of experience.
Priest
A priest is a person who, by virtue of his or her training, symbolizes a relationship with the spiritual, or, if you wish, the divine. Interaction with a priest is frequently highly ritualized, the ritual setting and roles providing an environment in which the patterns and prejudices of daily life are set aside and the priest can function for you as a representative of what you aspire to spiritually or religiously. Change comes through your trust in the ritual forms and using them to access what is in your heart.
Therapist
While there are many different approaches to therapy, the aim in therapy is to heal. Thus, a therapist helps you to heal from emotional or psychological wounds that you may have incurred in the course of your life. The therapist provides a healing environment, a place where old hurts can be touched, without your being re-wounded. Change comes through the power of the emotional connection you experience with the therapist. He or she supports you, through presence, attention, and caring, in revisiting old hurts so they can heal.
Coach
A coach is person who helps you change the way you behave, with the aim of making the way you do things more productive, more satisfying, less problematic, etc. A coach may well overlap with a teacher (teaching specific skills) and with a therapist (addressing to some extent the emotional issues that prevent you from changing your behavior). Change comes from your being willing to experiment with the different behaviors that your coach suggests and to see what works and doesn't work for you.
A consultant is a person who helps you solve a problem by bringing greater depth and breadth of attention, experience and/or knowledge to the problem at hand. The challenge for the consultant is to avoid being relegated to an ineffectual role (the hand-holder) or being held responsible for the problem if it can't be resolved (the scapegoat). Frequently, the consultant seeks to move to the teacher role in order to help his or her client see the problem (and hence the possible solutions) differently. Change comes from your working with a consultant as a partner, combining his or her knowledge and experience about similar problems with your knowledge of the particulars of your problem.
Mentor
A mentor is a person who has considerable experience, knowledge, and wisdom which he or she makes available to you. Where you learn specific areas of knowledge from a teacher, you learn how to implement that knowledge, how to live it, from a mentor. A mentor may also guide you in your path, in your career, for instance, but more generally, in the area of experience of the mentor. Change in you comes from your listening carefully to your mentor's experience and from the mentor creating opportunities for you to grow and develop.
Preacher
A preacher is a person who moves you emotionally, evoking such emotions as love, fear, awe, or joy through his or her words and presentation. A preacher typically works with groups, often large groups, speaking to them in such a way that they are moved emotionally, inspiring them to go beyond what they ordinarily think themselves capable of. Change comes about either through faith (opening to new possibilities) or belief (solidifying one's convictions) in the preacher or what he or she is saying.
Guide
A guide is a person who knows the territory, is able to find a path, and protects you, as much as possible, from danger on the path. A guide is a good person to be with when you are going into to territory that is unknown or unfamiliar to you. Think of a river guide, or a mountain guide. Change comes from following your guide's directions, not striking out on your own, but absorbing and learning from your guide until you know the territory and its challenges and can be guide yourself.
Now, what are you looking for in a teacher?
A guide is a person who knows the territory, is able to find a path, and protects you, as much as possible, from danger on the path. A guide is a good person to be with when you are going into to territory that is unknown or unfamiliar to you. Think of a river guide, or a mountain guide. Change comes from following your guide's directions, not striking out on your own, but absorbing and learning from your guide until you know the territory and its challenges and can be guide yourself.
Now, what are you looking for in a teacher?