The main difference between the Casio PB-80 and the Casio PB-80JR is that the PB-80JR is a "junior" version of the PB-80 that was designed to be more affordable for students.
In terms of features, the PB-80JR was slightly simplified compared to the PB-80.
However, despite these differences, the PB-80JR remains a very capable programmable calculator for students and beginner programmers.(chatGPT - march 2023)