Can anyone explain what the Bindings tab in the Pyro Bake Volume node is used for, and give an example?

The Bindings tab simply responsible to assign the right volume for the right functionality.

For example, Pyro Solver would output a volume named 'density', therefore the Smoke Volume set to 'density' by default to use that as the volume for smoke visualisation. Similarly you can choose what other volumes assigned for 'Scatter' or 'Fire'.

For the majority of cases, you can leave these settings on their default value.

Thanks, that makes it a little more understandable.