A domain is the address
Your domain is the name people use to reach a site. Registration gives you control of that name for the registration period; it does not automatically provide a website or mailbox.
Hosting runs or serves the website
Hosting provides the environment for your files and application. A static website and a PHP application have different requirements. List your runtime, database and storage needs before selecting an environment.
DNS connects the pieces
DNS records direct traffic to the appropriate services. Website and email records serve different purposes. Record the current configuration before making changes, especially when a domain already receives email.
Prepare the launch
Confirm the destination host, preserve existing email records, connect the domain, enable HTTPS and check the main pages and forms. Keep the previous configuration so you have a route back if something fails.