What is My Domain? | Salesforce
What is My Domain?
Using My Domain, Salesforce admins can define a subdomain within their Salesforce org. The subdomain name appears in all org URLs and replaces the instance name (such as na30). For example, you can brand your URL by naming the subdomain your company name, https://myCompanyName.my.salesforce.com/. My Domain is not the same as the custom domain for sites, communities, or portals. The domains are defined separately.