Bayesian credible intervals: Significant compared to what?

Thank you, but I’m still unsure as to whether the variables are compared to the pooled intercept or to each of the alpha-numerically lowest values of each variable? Put another way using my example:

Is the significance of “Nike” compared only to that of Adidas (the alpha-numerically lowest value of the variable “Shoes”) or to the whole intercept (“Adidas”, “Beginner”, “Old”, pooled)?