It's difficult to explain. If a person gives a description which is equivocal, I.E. could be thought of as more than one thing, then "if you will" is given after they have stated exactly what they meant. Using your example:
"Having an experienced host will help you feel safe"
That could refer to a number of different types of people. An experienced host could be someone who has ran a hotel for a number of years, or a person who often interviews people on talk shows. In your example though, the person has stated exactly what they meant with "a mentor", and then "if you will" follows this specification.
Student or Learner