client based vs server based subscription models

I’ve struggled to interpret this properly from the docs, would somebody be able to clarify what this actually refers to in practice please?

There are two subscription models. In one model (catchup subscription)
the client maintains the state of where it is in the subscription. In
the other model (competing consumers/persistent subscription) the
server maintains the state of the subscription.

There are many differences between the two models.
discusses may of them.

Ok understood, I thought it referred to something beyond this.