No. ShipStation is not a carrier or shipping company. ShipStation is a SaaS platform you can connect your postage provider accounts to so you can create the labels for your parcels. All parcels are shipped by those individual carriers.
ShipStation integrates with many carriers and postage providers, so you can use ShipStation to create labels for your preferred carriers. Please review our Carrier Integrations page to see which providers you can connect to ShipStation.