After you purchase a domain from a third-party domain provider, such as Google Domains, GoDaddy, or 1&1 IONOS, you need to connect your domain to your Shopify store. Connecting your domain points your URL to your Shopify store so that customers can enter that URL into their web browser to visit your online store.
After you connect your domain to Shopify, you still use your third-party domain provider to manage your domain settings, pay for your domain, and renew it.