I, an aroace person, also dont get it bc those do both contradict each other (as far as ik but I'm just some rando on the internet). Bi/pan (in short) means that u feel romantic/sexual (either or) attraction to anyone, while aroace (in short) means the u feel no romantic attraction (aro) and no sexual attraction (ace).
Ps. This is probably a not so good template to discuss this issue