On the Details page you can drill into the details for the individual fields (Guide and TripGrade) and interactions:

At the top of the details page, you should notice that Watson indicates the algorithm it used to find the insight and why:

TipGrade is a categorical target, so a logistic regression based approach is used.

If you click on the preceding terms (categorical, target, or logistic regression), Watson defines the term (and gives you a link to more details on the topic):