Custom Domain - Domain Registration in Salesforce

Custom domains allow customers to host their Salesforce Sites or Community on a domain name.

Add a subdomain to your Salesforce org URL with the My Domain Salesforce feature. Having a subdomain lets you highlight your brand and makes your org more secure. A subdomain is convenient and allows you to personalize your login page.

Your domain name uses standard URL format, including:
Protocol: https://
Subdomain prefix: your brand or term

For pros and cons, check

1. Go to Setup --> Administer --> Domain Management --> My Domain.

2. Check the availability of your domain name.

3. Check the terms and condition checkbox.

4. Click "Register Domain" button to register your domain.

5. Test it.

6. Click "Deploy to users" button so that other users can also use the same domain.