Shadowban from what I understand is being banned without knowing. You can interact with the community as if you weren't banned, but your votes won't count and your comments won't show up. But you feel like you are still participating.

Shadowban on reddit was apparently global on certain scenarios because there was a sub to test if you were shadowbanned.

I don't know how this global shadowban worked because from time to time I got messages from certain communities saying I was auto-banned from there for engaging in another community.