On the different mentor profiles, you'll generally see what kind of services a mentor can do for you. Here's what they mean in detail:
The ability for students to chat with their mentor. Every mentor has to provide this service.
The mentor sets weekly goals and activities for the student. These can consist of small challenges and project or reading material. They are supposed to help towards reaching a bigger end goal.
The mentor is available for 1-on-1 phone calls. How often these occur is meant to be agreed on between the student and the mentor. They can be irregular and spontaneous or scheduled weekly/biweekly/monthly.
The mentor is willing to help the student with code, by giving them hints or even pointing out or fixing smaller bugs. Important: Mentors are not freelancers! Wanting them to implement components or help with a commercial product is not tolerated.