Moving a website: what needs to move besides the files?
A website migration can be simple, but only after you know what is attached to the old hosting account.
Website files
Images, themes, plugins, scripts and other files are the visible part of a migration.
The database
WordPress and many other content-management systems keep pages, settings and users in a database. Copying files without the database does not copy the whole site.
DNS
DNS tells browsers and mail systems where to go. A website can be fully copied to a new server and still show the old one until DNS is changed.
Mailboxes may be hosted with the same provider as the website. If you change DNS without checking mail records, a website move can accidentally interrupt email.
SSL and final checks
The destination needs working HTTPS, and the live site should be tested after the switch. Forms, logins and important pages deserve a real check rather than assuming the transfer succeeded.