ShipStation is an order management suite that collects your physical sale information from all of your merch stores and lets you manage them in one place. Bandcamp connects directly with their system to help you fulfill your orders. Label accounts come with a ShipStation enabled; others users can request that by getting in touch.
Once ShipStation syncing has been enabled for your Bandcamp account, you'll see a set of credentials on your Bandcamp Settings page. These credentials sync your Bandcamp merch orders with your ShipStation account. More information on making the connection can be found here, and ShipStation has some additional tips on using their Bandcamp integration.
It's worth noting that marking orders as shipped within ShipStation skips Bandcamp's shipping notification emails. You'll want to make sure those are enabled on ShipStation's end to ensure your fans are receiving their order info.