Need Info on the signing.pem and cas.pem file

I am trying to setup ziti from scratch ( 1 controller , 2 routers (priv/pub) ) and created the pki using the ziti cli. I was parallely looking at the ziti setup that i created using the express install. Root ca, intermediate ca, signing ca, all these certs makes sense to me, but i came across a signing.pem and cas.pem cert which i am not sure where they came from and what are they used for, please help

I made an explainer video a while back here https://youtu.be/Fk2sE0ydVo8

I also had a discussion with another community member along these lines a few months ago here What does the quickstart do that I need to do myself? In there that video walks through this file https://raw.githubusercontent.com/dovholuknf/openziti-compose/main/from-scratch.sh which is the steps the express install does, narrated.

Let me know if that doesn't get you the answers you need. cheers