How do you pay for buses in Kyoto?

Excuse me, could you please elaborate on the process of paying for buses in Kyoto? I'm a bit unfamiliar with the local transportation system and would like to know if there are any specific methods or machines that I should be aware of. Are cash payments accepted, or do I need to purchase some sort of prepaid card or ticket beforehand? Additionally, are there any discounts or passes available for frequent travelers? Thank you for your assistance.