Every Artist on CO:CREATE sets their own policies.
Artists are all running their own businesses, and may handle things differently at their own discretion.
Policies can cover a wide variety of things, most commonly:
How Deposits work
Rescheduling, cancellations, or no-show policies
Whether or not they're accepting cover-ups
Policies are displayed on Artists CO:CREATE profiles, and right before you Book.
On an Artist's profile, you'll find their policies under the More tab. You'll need to review and agree to your Artist's policies right on CO:CREATE before you pay to Book with an Artist, to avoid surprises.