How do zero-conf channels work?

[Bitcoin]

How do zero-conf channels work?

What zero-conf channels are seems pretty straighforward (correct me if I'm wrong) -- channels that are immediately usable without needed confirmation on the blockchain. These are very useful since Alice can get Bob set up on Lightning without needed to wait for confirmation.

If there are different variants, can you describe how each works,trust assumptions, and possible drawbacks/attack vectors?

Source: How do zero-conf channels work?