The priors are the probabilities you assign to hypotheses before you receive any evidence for or against that/those hypothesis/hypotheses. [;Pr_{i_{z1}};] and [;Pr_{i_{z2}};] are the posterior probabilities on [;Pr_{i_1};] and [;Pr_{i_2};] respectively.
The priors are the probabilities you assign to hypotheses before you receive any evidence for or against that/those hypothesis/hypotheses.
[;Pr_{i_{z1}};] and [;Pr_{i_{z2}};] are the posterior probabilities on [;Pr_{i_1};] and [;Pr_{i_2};] respectively.