Leon here from Shopify Support.
The .myshopify.com URL that shows for your store is the account name, but you can add a custom domain to mask this, so your customers will only see the domain you own, not the myshopify.com.
If you already own a custom domain, you can add that to your Shopify admin by going to Sales Channels > Online Store > Domains. Then click the 'Add existing domain' button in the top right.
Once you've added the domain to your Shopify admin, you'll need to change the DNS settings from your domain host. In the DNS settings change your root domain (without the www) to have an A Record pointing to 18.104.22.168, and the Cname pointed to shops.myshopify.com.
I've simplified it, but this process is explained in greater detail in this guide.
If you do not already own a domain, you can purchase one through your Shopify admin for as low as $13 per year including whois privacy protection.
If you have any further questions, please let me know!
I do have a question? I am new using shopify, your explanation was excellent, but my question here is, if I buy a custom domain through shopify, can I transfer the custom domain to be the URL so I can use the domain that I already have for my customer to see the .com. because the new domain that I will get wont have the .com because is already in the myshopify.com. Now the name of my store will have .us or .shop etc, and I want my customers to see the name of my store.com