We all know that mentors are important for professionals at all career levels. They can open doors, suggest career paths, make introductions, teach new skills, and provide honest feedback. Mentors are especially important for entrepreneurs. Getting trusted advice as you’re launching a business can be invaluable, and so is knowing that you have someone to turn to when you’re facing a difficult decision.

But not all mentors are created equal. We sometimes think of a mentor as a close friend or colleague who guides us through our career decisions, or a formal relationship with someone we look up to. The reality is that there are opportunities to learn from people in a variety of areas and positions. The trick is to identify which type of mentor you need for what situation, and then start building your network.

The Peer Mentor

This person is often overlooked as a mentor because they may simply be a friend or colleague. The peer mentor is likely doing work that’s very similar to yours or on the same career path as you. Either way, the peer mentor is someone you can talk with without fear of reprisal. You can vent your frustrations and talk openly about your struggles, and know that it won’t affect your relationships with clients, vendors, or investor. A peer mentor is someone who will celebrate your successes with you, validate your struggles (because they understand where you’re coming from), or brainstorm through a difficult situation. And because they’re a peer, this might mean that you vent over a pint—either beer or ice cream—and know that they’ve got your back.

The Ad Hoc Mentor

Also known as a short-term mentor, this person gets called in when the situation requires their particular expertise. Think of them as the pinch hitter of mentors. They may not play every game, but they’re always on deck and ready to help when needed. And more often than not, when they do step up, the results are pretty good.

Use the ad hoc mentor for those areas in which you need expertise, but not on a regular basis. Ad hoc mentors can give you a crash course in reading financial statements or helping you understand the basics of a solid marketing plan. This is informal knowledge-sharing, and this type of mentorship generally ends when the knowledge has been shared.

The Challenger

It’s way too easy to surround yourself with people who agree with you, support you, and give you nothing but praise. But we all know that to grow and succeed, there has to be an element of working outside of your comfort zone. As the name suggests, the challenger mentor will do just that. This person should challenge your way of thinking, question your goals and your process, and require you to justify what you want to do. Their goal isn’t for you to fail. On the contrary, they’ll be cheering for your success on some level. But they’re going to help you get there by forcing you to let go of perfection, fine-tune your idea, and approach your work with a different perspective. Your relationship with this mentor should help you hone your ability to receive feedback—and then turn it into positive action steps.

The Coach

This mentor is the closest thing to the image we may have in our mind. The coaching mentor is a seasoned professional, someone who has experienced the many highs (and some of the lows) of being an entrepreneur and is willing to share their lessons with you. With this mentor, take advantage of the depth of their experience, and ask them to help you strategize big-picture issues, break down business goals that have significant impact, or identify opportunities for funding.

Regardless of the mentor type or the issues they help you navigate, be sure to let them know that you appreciate their guidance. People who mentor do so because they want to help others grow, so finding a way to tell them how they’ve helped you will go a long way. And when you find yourself in a position to mentor someone else, remember how a mentor made a difference in your life and pay it forward.