Migration is the process of moving your data and content from one site to another. It is a comprehensive process involving several steps. We generally migrate if we want to switch to a more modern website, whether we change our domain name or our entire server.
As for a 301 Redirect, as the name suggests, the visitor is permanently redirected to the new URL. The domain name you entered in the browser bar will be replaced by the new domain name. This allows you to preserve the history of the site for the benefit of your new URL. The more accurate this redirect is, the more your new content will retain its SEO potential.